In 2014, James Gunn dropped a game-changer on the MCU in the form of "Guardians of the Galaxy." Up until that point, Marvel Studios treated us to tales of Iron Man, Hulk, Captain America and Thor. The latter introduced us to the Nine Realms of existence, and we also got exposed to space with the Chitauri from "The Avengers." This left the cosmic door further ajar, which Gunn took full advantage of, firing off his ensemble of heroes to safeguard space.

RELATED: Guardians Of The Galaxy: 15 Ways The Film Improved On The Comics

The look, feel and overall vibrancy of his movie stood out from other Marvel Studios films, and had a distinct flair that fans hadn't seen before, but certainly wanted. The sequel looks just as, if not even more, bombastic. With that in mind, CBR decided to look back at 15 reasons why the first "GOTG" film changed the landscape of the entire MCU!

SPOILER WARNING: Major spoilers ahead for "Guardians of the Galaxy" and other MCU movies

15 A UNIVERSAL DOOR OPENER

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In the "Thor" movies, we saw the Nine Realms of the World Tree, with Jotunheim (the frigid home of the Frost Giants) and Svartalfheim (the arid home of the Dark Elves) being the main ones explored. Apart from these, the MCU hadn't really ventured or explored any other world or realm, Asgard notwithstanding. "GOTG," however, unlocked the door to the universe and truly showed us what lay beyond that portal that the Chitauri came through at the behest of Loki.

We found out he got the army from Thanos and eventually saw the big baddie in space smiling in "The Avengers" post-credits, so we knew galactic tales were awaiting. Gunn then took us for a bigger ride than we anticipated, showing us the full breadth of space, and having us traverse the drama and dangers it possessed with Peter Quill (aka, Star Lord) and his team. Through their journeys against the Ravagers, outrunning Ronan (Thanos' Kree lackey) and meeting with the Nova Corps and Collector, we got to see just how expansive the MCU would become.

14 THE RELUCTANT HERO

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The MCU had already established who the Avengers were as a team, and individually it was obvious each was meant to, and wanted to, be a hero. Steve Rogers took the super-soldier serum to become a paragon of virtue, while Tony Stark and Thor, despite their arrogance, were always going to use their gifts to walk the heroic path. Even Black Widow, Hawkeye and Hulk took that conscious decision to use their talents to protect the world. Quill, however, simply fell into his situation and decided to roll with the punches.

It was never his aspiration to be a hero as he was purely a scavenger and treasure hunter trying to survive. Quill owed no one anything because everything he ever had was snatched away from him when he was taken off Earth. While the Avengers harbored Earth-saving hopes and dreams, Star Lord simply had a gun and an appetite for quick money, which made him very relatable, and even more altruistic when he decided to make the sacrifice to save the galaxy with his misfit friends.

13 MINIMAL ROMANCE

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It was a breath of fresh air to finally get an MCU movie that didn't harp on about romance. The "Iron Man" movies overdid it with Stark and Pepper Potts, while Steve Rogers never lost his affinity for the Carters. Thor also had to contend with a lot of drama with Jane Foster, while Bruce Banner couldn't get his mind off Betty Ross. Yeah, it's pretty obvious the MCU needed a lot of couples therapy.

However, Quill, while he did begin to develop feelings for Gamora, managed to play it cool and not go overboard with her (though sometimes not for lack of trying). There were some moments where their chemistry made you think Gunn was going to stray into romantic territory but he dialed it back well. It was endearing but we were glad the team ended up sticking to the mission at hand instead of engaging in love antics. We can't wait to see them explore this potential relationship in the sequel, though.

12 CHANGED UP THE POST-CREDITS GAME

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Usually, the mid or post credits of any MCU movie would continue a snippet into Thanos' lust to conquer the galaxy, the whereabouts of the Infinity Stones, or hint at where the next hero or villain would be coming from. It was a tried and tested formula that worked wonders since Nick Fury stepped out of the shadows in "Iron Man" with his Avengers initiative, and honestly, it's been so successful that other blockbusters adopted it (including the "Fast and Furious" franchise).

RELATED: 15 Best Post-Credits Scenes In Comic Book Movies

Gunn, however, poked fun at the trend and in the process gave Marvel fans a huge throwback when he showed the Collector kicking it with Howard the Duck. This would actually reignite the cult favorite's career as Howard even got back into the Marvel Comics limelight, most recently written by Chip Zdarsky. It was a cheeky scene that left everyone in disbelief as they wanted something much more serious, but that still couldn't stop them from chuckling at Howard's pep and attitude.

11 TRUE COMEDY

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This movie definitely stuck to the tone that we saw in modern "GOTG" comics, especially the ones from Dan Abnett and Andy Lanning. Gunn shaped his film with a lot of fireworks but he laid on a lot of crazy humor. Chris Pratt delivered a near-perfect depiction of Star Lord, and outside of all his jokes, there was Rocket Raccoon and Groot, who kept you laughing throughout with their one-liners (especially in Groot's case). Drax being so oblivious and literal was also another high point.

It was hard to believe all this comedy was packed in, yet worked so well. Even when Iron Man cracked his jokes, or Thor quipped something, it still felt like an action movie, but "GOTG" was so cleverly done that it came off as a comedy, with action spliced in, not the other way around. This constant dynamic was remarkable and came full-circle in Quill's unbelievable dance-off with Ronan in the finale!

10 BEYOND THE AVENGERS

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All we knew about the MCU at this point was that heroes existed who were going to work together to fight Thanos. Everything was Avengers-centric, and with everyone on Earth, bar Thor, it felt somewhat grounded and small in scope. Gunn, however, showed us worlds where in every space bar or port, you could meet aliens or other ethereal beings that would be considered a superpower back on Earth.

It was as diverse as it was dangerous, as seen when the Guardians were imprisoned and had to break out. Even Yondu's rapscallions were pretty scary. And if that doesn't worry you, what about Ronan's crusade and followers? Earth has a lot of threats, but "GOTG" showed that the planet was just a small fish in a big pond because who knows what lurks beyond Thanos? We glimpsed the Celestials as well, got a look at Knowhere, and dove into the Nova Corps, which extended the reach of the MCU. That got us thinking maybe we could even see the Cancerverse from the books! The door truly was blown wide open and exposed us to so much more.

9 THE FIRST TASTE OF HEROIC DEATH

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Some would say Bucky was the first taste of heroic death in "Captain America: The First Avenger," but he was more a partner to Steve than an actual Avenger or stalwart of the MCU. Groot, though, was an all-out Guardian when he perished in Gunn's finale, saving his team in the process. It was a heartbreaking moment that brought tears to all our eyes because we were all laughing constantly at his antics, especially with Rocket.

When Rocket began to cry over losing his bestie, the feels hit home even harder. It felt like we really lost a teammate and Gunn pulled it off so well. It was a true sacrifice and came off natural, like a lesson the team had to learn to be mature in the space wars to come. Lo and behold, we got Baby Groot, reborn and shaking it once again! Groot's dance with death was brief but it showed that the stakes were high. We couldn't imagine the team without him, and it showed that no matter how tough the Guardians were, it was a family of heart and soul.

8 THE THANOS IMPERATIVE

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This film saw Josh Brolin debut as the Mad Titan, and he imposed himself powerfully. He came off as truly sinister, intimidating but still with a slight sense of humor as he laid the law down for the likes of Ronan and Nebula in their pursuit of Quill's team and the Orb (Infinity Stone). When he threatened to "bathe the star-ways in blood," we all got chills down our spine because it was Thanos truly signaling his intent at galactic domination.

Before that, he was merely in the shadows, smiling and conniving, but now we saw him in his glee, treating the cosmic universe as playthings from his throne. We didn't expect so much screen time from him, and even when he communicated via hologram (ala the Emperor in "Star Wars"), Thanos still managed to inflict a sense of dread. It set the stage perfectly for the "Avengers: Age of Ultron" mid-credits where he donned an Infinity Gauntlet to continue the quest himself.

7 A TRUE SPACE SAGA

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"GOTG" proved that it was a space gem, ready to rival legendary franchises such as "Star Wars" and "Star Trek." It was all about exploration to the depths of the unknown, meeting new species and interacting with them, staving off space cults, pirates and thugs, and of course, banding together like Robin Hood's merry crew to save the day when destiny tossed the opportunity their way. "GOTG" truly ended up being otherworldly and boldly went where no comic book movie went before in a galaxy far, far away. And so on...

Watching Quill, as a dashing Han Solo-esque debonair, and his team on their badass raids and escapades set the bar high for other movie studios who want to do space sagas. It had tons of action, excitement, suspense and humor, and still managed to remain a fun, family film. It also didn't go back to Earth, which was a huge breath of fresh air from the "Thor" movies, which always managed to take you away from new realms and experiences.

6 THE CUTE FACTOR

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The MCU didn't bring the cute factor to viewers just yet, but when Groot hit the screen, it was off the charts. It was a smart move, and sure to be amplified in the sequel with Baby Groot dancing, setting off bombs and other forms of misadventure. But in this film, it was all about his charm and innocence. When he said, "I am Groot!" it was adorable, which made him kicking ass even funnier.

The same could be said for Rocket, who was quite endearing, even when his violent tendencies acted up. After all, just look at his cute raccoon face! It's hard to take him seriously as a mercenary, which is the kind of underestimation that costs his opponents hands and legs. Last but certainly not least, Drax, in all of his scenes, displayed an oblivious nature where he took things way too literally, that you couldn't help but giggle. Seeing former WWE superstar, Dave Bautista, in this role had us cracking up because it was something you'd never ascribe to his character.

5 RAGTAG MISFITS INSTEAD OF SOLDIERS

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In the MCU, all the heroes were trained to be soldiers, and those who weren't (like Hulk) could have filled such shoes as a powerhouse at any time. Even the anti-heroes like Widow and Hawkeye leaned towards the light. The Avengers, after all, were an offshoot of "S.H.I.E.L.D." and their military vision to protect Earth. The Guardians, however, were lumped together by greed and luck, and were simply a ragtag band of misfits who realized if they didn't save the day, they wouldn't have a galaxy to profit from.

They weren't heroes brought together by a singular honorable objective. They were selfish, not selfless. They just wanted to get by, and get rich. It just so happened they had the talents, which when strength in numbers factored in, made them an unconventional squad that could parallel Earth's mightiest. Their banter, love-hate relationships, chemistry, and overall camaraderie make them a unique option but one we're glad to be stuck with. Their methods don't follow the heroic rulebook, which makes them the best option to be our space Avengers, where things get much more rowdy than on Earth.

4 FULL CREATIVE CONTROL AND FREEDOM

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"GOTG" gave the first impression of a director having full creative control and freedom to bring his vision to life. Even in his style of trailers and choices of music, it just felt like this was Gunn's film. There wasn't the drama that plagued Jon Favreau after the contentious "Iron Man 2," or which Kenneth Branagh and Alan Taylor were rumored to have gotten on their "Thor" films. Even Louis Letterier didn't seem too happy after "The Incredible Hulk," and there were early rumblings that Joss Whedon would head out after "Age of Ultron."

From the behind-the-scenes and set photos, Gunn and Pratt looked like they were leading the charge with a sense of joy, and the rest of the crew beamed about this direction. Gunn was able to place his signature and stamp the film in such a way, it would end up as the most unique movie from Phases One and Two. The Russos did remarkably well on "The Winter Soldier" but Gunn's movie felt like something unbelievably new, collaborative and fresh. No wonder he wrote and directed the sequel, and will do the same for the third chapter!

3 THE INFINITY STONES ORIGINS

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Prior to this film, all the MCU told us about the Infinity Stones was that Thanos wanted to harness their power to rule the galaxy. The Collector went in depth into them and we saw their existence at the point of the universe's creation and how they were weaponized with the ability to wipe out civilizations. We also saw the Celestials wielding them, which was the catalyst to Quill's team realizing that things were much bigger than they first thought.

Gunn broke it down brilliantly and shaped the doom and gloom to come with Thanos if he got all the Infinity Stones. Linking the Nova Corps in as part of the defense wave against Ronan also showed how dire circumstances were. What makes this even more crucial is that none of the Avengers were as yet privy to this knowledge, which made the Guardians a very apt title as they were front and center as the first wave to stem Thanos' tide.

2 THE MUSICAL REVOLUTION

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"GOTG" showed just how much character scores and soundtracks could add to a film. From the marketing to the movie itself, Gunn knew what he wanted to do off the bat. Quill's awesome mixtape further pushed fans in this direction, as it was a nostalgic trip down memory lane for lovers of the walkman. Blue Suede's "Hooked On A Feeling," The Jackson 5's "I Want You Back," and David Bowie's "Moonage Daydream" helped create an atmosphere of humor, intrigue and wonder.

They were just the tip of the iceberg as Gunn used artists such as Marvin Gaye and Rupert Holmes to continue bringing a sense of romance, comedy and action. The soundtrack was very diverse and that's because the movie traversed the entire emotional spectrum, and would have needed a like-minded sound bed to reflect these oscillating feelings. This surely influenced the "Luke Cage" series and Gunn's "Guardians of the Galaxy: Vol. 2," because it's clear music adds more personality to the product.

1 THE VISUAL AESTHETIC

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Apart from the film's tone, it was Gunn's visual aesthetic that really set it apart from the rest of the MCU. Marvel Studios have never shied away from color as Warner Bros. have with the DC movies, but Gunn took it to a next level with a resplendent color palette that made "GOTG" pop like a kaleidoscope. He made the depths of space vibrant, memorable and attractive, as seen on Knowhere, Xandar (home of the Nova Corps), and even with aliens in the film such as Thanos, Gamora and Nebula.

This appears to have been elevated for the sequel because the MCU clearly knows that to make the Guardians stand out in their space endeavors, they need to brighten their direction up even more. Gunn profoundly laid the groundwork and executed his vision in spades. "GOTG" was, in general, a visually attractive film, which ended up popping as a funny, relentless, and action-oriented treasure hunt.

Thoughts on our picks? Let us know in the comments which segments of "GOTG" changed the MCU for you!