Superhero cartoons have been around almost as long as superhero comics have, the first animated adaptation being the Fleischer/Famous Studios Superman series that ran from 1941-43 -- just eight years after the character's creation. Not only did it set the bar high for every superhero cartoon following it, but it also proved right from the get-go that adaptations in other media could reciprocally shape the characters and worlds they brought to life on the small screen. For instance, it was the '40s serial that popularized the "it's a bird, it's a plane" tagline for Supes. Decades later, Batman: The Animated Series built on this legacy by distilling and adding to the Dark Knight's mythos to Emmy-winning acclaim. Over 25 years later, it's still considered by some to be the finest interpretation of Batman ever made.

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Other classics like X-Men: The Animated Series, Justice League, The Powerpuff GirlsSamurai JackBatman Beyond, and the cheesy oeuvre of He-Man and the Masters of the UniverseThunderCats and Teenage Mutant Ninja Turtles are all fondly and widely remembered. But, while there are some cartoons that stand the test of time, there are others that shone brightly before fading into obscurity. Sometimes they were too ahead of their time, sometimes they were overshadowed by their predecessors and sometimes they were killed off by networks before they even have a chance to really spread their capes and fly. These brilliant superhero cartoons may be gone, but they certainly shouldn't be forgotten.

15 AVENGERS: EARTH'S MIGHTIEST HEROES

Avengers Earth's Mightiest Heroes

The Avengers have been a mainstay in TV cartoons since the '60s, though it took them a surprisingly long time to actually assemble. 1966's Marvel's Super Heroes had Captain America, Iron Man, Hulk, Thor and Sub-Mariner star independently in one episode each per week. From then on, they made cameos in other Marvel shows, until finally appearing together in 1999 for Avengers: United They Stand.

Avengers Assemble, from 2013, which was created to build on the success of The Avengers film, is a solid show, but arguably its predecessor, 2010's Earth's Mightiest Heroes -- which was canceled to make way for Assemble -- was the superior adaptation. With the pitch-perfect mix of gags and action fans have come to expect from the live action versions (not to mention a killer theme song) the show's cancellation meant it sadly slipped off the radar.

14 WOLVERINE AND THE X-MEN

Wolverine and the X-Men

X-Men: The Animated Series was a very hard act to follow. It ran for an impressive five Seasons in the '90s to both huge critical and commercial success and introduced a whole new generation of X-fans to Marvel's mutant heroes. X-Men: Evolution did the smart thing in 2000 and deviated completely from its forerunner, rather than try to replicate the formula. It also deviated a lot from the official canon to mixed degrees of success.

Wolverine and the X-Men, however, the show that followed Evolution in 2009, was a far better spiritual successor to X-Men: TAS, and a far superior show to Evolution. Featuring an older, Xavier-less cast, the show had enough maturity to satisfy older fans, while delivering enough suspense and heart to draw in younger ones. Criminally, it was canceled right after teasing an Apocalypse arc in its Season One finale, which explains its relative obscurity now.

13 FANTASTIC FOUR: WORLD'S GREATEST HEROES

Fantastic Four World's Greatest Heroes

If you really want to get depressed about Fox's live-action treatment of the Fantastic Four, compare and contrast the 2015 reboot film to any episode of Fantastic Four: World's Greatest Heroes. Even if you prefer the team to be a little more on the grittier, dysfunctional side, it's hard to not be completely charmed by the bright colors and zippy pace of this sadly forgotten series from 2006.

The Fantastic Four have had their own animated shows in the '60s, '70s and '90s, all of poor to passable quality. It's a shame, then, that arguably the most faithful -- and most fun -- series of the '00s is the least well-remembered. Its anime-esque style gave it a fresh energy while it's espionage-themed opening credits were a fitting tribute to the spirit of the decade that Marvel's First Family were created in.

12 SPIDER-MAN: THE NEW ANIMATED SERIES

Spider-Man the new animated series

Spider-Man has been the star of many well-loved animated adaptations. The '60s series has provided a wealth of meme-able material, while the '90s Animated Series is considered not just the best Spider-Man cartoon, but one of the best superhero cartoons, period. He's barely left our big or small screen since then. Arguably, 2007's Spectacular Spider-Man is a close contender for "the best but forgotten" Spider-Man series.

But, that unwanted crown should really go to the even more forgotten New Animated Series from 2003. Starring the voice of Neil Patrick Harris, the show was made for an MTV audience and served as a sequel series for the first Spider-Man movie, using the Ultimate Spider-Man comics as inspiration. Though fans and critics appreciated its maturity (and the CG animation still holds up surprisingly well) it was cruelly canceled after Season One.

11 SILVER SURFER

Silver Surfer The animated series

This short-lived 1998 series served, if nothing else, as a strong animated translation of Jack Kirby's trippiest art. The use of a commanding narrator's voice was also a great slice of nostalgia. Featuring a wide range of cosmic characters -- Uatu, Adam Warlock, Nebula, Drax The Destroyer and Ego The Living Planet -- the show took viewers far into the depths of space and relatively obscure Marvel mythology for a young, impressionable audience.

Though it did take liberties with the source material, the showrunners didn't shy away from socio-political issues that are central to the character's most pivotal stories; condensing some of the Silver Surfer's most epic exploits into digestible single episode segments with mesmerizingly psychedelic animation. Its cancellation after just eight episodes was apparently due to a legal battle between Marvel and Saban.

10 AEON FLUX

aeon

This pioneering MTV series spent three Seasons pumping experimental, erotically-charged images of super spies in skin-tight leather into unsuspecting viewers heads between 1991-5. Looking like an insane cross between Ghost In The Shell and an Egon Schiele painting, and burying its plotlines within layers of philosophical techno-babble, it's no wonder that the series is considered now to be a cult classic, rather than a well-known mainstream gem.

Today, most people are probably more familiar with the 2005 live-action movie adaptation starring Charlize Theron, which is considered by most fans of the cartoon to be a completely separate entity. Aeon Flux's creator, Peter Chung, called the film a "travesty" during a LiveJournal interview in 2006 and decried the misinterpretation of Aeon's character as a heroic action star.

9 MIGHTY MOUSE: THE NEW ADVENTURES

Mighty Mouse New Adventures

Between 1942 and 1961, Mighty Mouse -- the rodent answer to Superman -- starred in a whopping 80 films, which were then repeated on Saturday morning TV up until 1967. After over a decade-long absence, the superpowered mouse was revived by Ralph Bakshi for an all-new series in 1988 that gave Mighty Mouse a civilian identity and a more adult flavor. In fact, this mature sensibility landed the show in hot water when a scene from "The Littlest Tramp" was mistaken to allude to cocaine use.

Unfortunately, this controversy is probably what the show is best remembered for, which is a shame considering the huge cultural legacy of the character and The New Adventures as a production. Staff members included Bruce Timm, John Kricfalusi and writers, directors and animators who would go onto to work on The SimpsonsFuturamaTiny ToonsPowerpuff Girls and Disney/Pixar movies.

8 MEGA MAN

Mega Man

Based on the iconic video game character and series of the same name, this 1994 series that was an American/Japanese collaboration was at one point the highest rated kids show on TV. Despite being a hit, it was canceled in 1995 after just two Seasons due to... guess what? Poor toy sales. After all, there's no other reason for Bandai and Capcom to bother pouring money into a cartoon.

There was also no reason that an extended toy commercial needed to necessarily be as good as the show was. Video game adaptations also have a history of being notoriously sub-par but Mega Man -- while far from perfect -- beat the odds to be a fun, peppy watch with fast, fluid animation. In fact, the opening credits alone are worth watching if you want to recreate the feel of an acid trip at a '90s techno rave.

7 SILVERHAWKS

SilverHawks

Set in the 29th Century, SilverHawks followed the titular team of cyborg humans sporting metallic wings. It was created by the same studio that produced ThunderCats -- and it really shows. Intended to tap into the same market that was lapping up Lion-O and company, the show recycled much of the same elements while leaning more into sci-fi than fantasy influences.

It even reused most of the ThunderCats voice actors and had a supervillain called Mon*Star, which sounds a lot like... Well, you know. Despite being a copy-and-paste job, SilverHawks should be as well-remembered as ThunderCats. It had more than enough '80s cheese and charm of its own and the externally-produced Japanese animation holds up better than others of the era. It also featured an evil henchwoman called Melodia who looks like Lady Gaga as a Space Bard.

6 HARVEY BIRDMAN, ATTORNEY AT LAW

Harvey Birdman, Attorney At Law

Along with Space Ghost: Coast To Coast, Harvey Birdman, Attorney At Law was a satirical reimagining of a forgotten superhero cartoon character from the '60s -- the eponymous Birdman, from the series Birdman and the Galaxy Trio. While it delighted in delivering harsh truths about beloved Hanna-Barbera characters, its 2D animation style also played affectionate tribute to them.

Strangely, kids weren't that interested in a show about a retired superhero working in a law firm, and the series moved from Cartoon Network to Adult Swim, a far more comfortable fit for its style of humor. Unfortunately, Adult Swim's (then) niche audience meant the show isn't as widely known as it should be today. Along with Space Ghost: CTC, it helped define the channel's surreal and dark sense of humor and trademark parodying of pop culture that would become a springboard for hits like Rick & Morty.

5 THE MAXX

The Maxx

Based on the Image comic book series of the same name, created by Sam Keith, The Maxx was another of Liquid TV's experimental -- and sadly obscure -- cartoons produced for MTV, following Aeon Flux in 1995. In a similar vein to the latter, The Maxx was uncompromising in its attempt to almost dare viewers into watching it rather than inviting them into something comfortingly familiar. Suitably, it was aired as part of "MTV's Oddities" block.

Unlike most other animated comic book adaptations, the show bravely chose to mimic the art style of the source material rather than smooth it out into a more standardized cartoon one. It also didn't shy away from the comic's socio-political themes: The Maxx is a hulking homeless superhero who doggedly protects a suffering social worker called Julie Winters, to whom he feels psychically connected.

4 STATIC SHOCK

Static Shock

Though Static Shock had a slightly mixed reception during its four Season run between 2000-4, its legacy is an important one. Masterminded by Dwayne McDuffie -- and serving as his platform for a successful career writing for animated TV -- the character of Static Shock was the wise-cracking, younger version of the Milestone/DC Comics character, Static.

The titular hero, also known by his civilian alter ego name, Virgil Hawkins, gained his powers the old-fashioned way -- he was accidentally mutated by weird chemicals. He also served as one of the few cartoon superheroes of color, and the show's social themes and the hip-hop influenced soundtrack garnered praise for championing multiculturalism. Though fondly remembered by those who originally watched it, Static Shock could definitely do with a lot more love.

3 TEENAGE MUTANT NINJA TURTLES (2003)

TMNT 2003

Teenage Mutant Ninja Turtles are still a huge deal in pop culture, partly thanks to the endless cycle of animated adaptations that are inevitably churned out every couple of years. The first series lasted from 1987-96 and its monstrous success and cultural impact still overshadow everything that has come after. The original cartoon also sanitized the monochrome grit of the comics effectively for a young audience.

The 2003 series that followed it brought some of this darkness back to arguably greater effect -- but still in keeping within kid-friendly boundaries. As such, Michelangelo became more distinctive as the "funny guy" while his brothers dropped the pizza-gobbling and gags to become more serious and layered. This was down to Mirage Studios -- the characters' publisher -- taking back creative control and co-production duties.

2 THUNDERCATS (2011)

ThunderCats

When it comes to cartoon classics, ThunderCats -- for all its ridiculousness -- remains a high-ranking favorite. Because of its lauded place in pop culture history, any subsequent reboot or reimagining has its work cut out for it, proved by the criminally underrated and under-watched 2011 retelling. Like the 2002 He-Man reboot, the show aimed to scale down the '80s cheesiness into something more believable.

This meant Lion-O and the Cats were recast as rebel freedom fighters trying to expel Mumm-Ra and his Lizard army from power after their hostile takeover of Thundera. The show's range of anthropomorphic animal species gave it license to address issues like racism and colonialism in less patronizing terms than the original, and its focus on complex character relationships was impressive. Reasons behind its premature cancellation remain a mystery.

1 TODD MCFARLANE'S SPAWN

Spawn

You know you're in for an interesting ride when a cartoon begins with a disclaimer for "graphic violence" and "nudity." Originally aired at midnight on HBO from 1997-9, Todd McFarlane's Spawn was everything you'd hope for from a Spawn adaptation -- brooding, violent and atmospheric. The opening title sequence, teasing fleeting snapshots of the character whipping across a black backdrop like a horror movie phantom, is still spine-tingling to watch.

It's easy to see why an edgy character like Spawn was the perfect fit for HBO -- and vice versa. Perhaps if the show aired today, the mainstream success of anti-hero comic book characters like Deadpool coupled with the channel's own meteoric rise in viewership might have resulted in it reaching a wider audience. As it stands now, the show is a beloved but largely neglected classic.

Which great superhero cartoons do you think aren't as well-remembered as they should be? Let us know in the comments!