For decades, it was hard to get any big name actors to take part in a superhero project, so earlier projects focused on younger actors looking for a breakthrough role. That all changed in 2000, when veteran actors like Ian McKellen, Patrick Stewart and Famke Janssen were cast in X-Men, one of the first major superhero movies in the modern era of cinema. The cast along with a decent script and heavy-handed direction from Bryan Singer lead to one of the first comic book box office success stories ever. The rest of Hollywood would soon follow, harvesting comic books for television, feature films and animated specials.

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However, for every X-Men there's a Green Lantern. When it comes to source material that a mainstream audience isn't familiar with, casting is usually the key to making the project a hit. Bad casting can make a movie tank, no matter how good the script, CGI or direction given. This also goes for comic book television series, like Marvel's Agents of S.H.I.E.L.D. and especially for the superhero-centric Arrowverse on The CW which features dozens of superheroes and supporting characters every week. CBR takes a look at some of the Arrowverse's hits and misses when it comes to casting our favorite heroes.

15 BAD: DANIELLE PANABAKER AS KILLER FROST

Formerly a hardened criminal, the current version of Killer Frost featured in the pages of DC Comics is more of an anti-hero, never wavering on one side of the law or the other. A former S.T.A.R. Labs scientist who gains her powers after a thermodynamic engine explosion who then works with Professor Martin Stein on a way to control her abilities. To a certain extent, most of this has been translated into Killer Frost's story on The Flash.

While Danielle Panabaker has experience in the superhero department (she played in 2005's Sky High as a girl with the ability to manipulate plants), but when it comes to pulling off Killer Frost, Panabaker's performance often feels one-dimensional. We totally get her as Dr. Caitlin Snow, but it's her alter ego we have a problem with. Maybe now that they've started marrying her two identities, she'll get better at playing the part.

14 GOOD: STEPHEN AMELL AS OLIVER QUEEN/GREEN ARROW

Starting out as another orphaned billionaire turned superhero, Oliver Queen became the Green Arrow to fight crime in his hometown of Star City. He's a frequent member of the Justice League and is often seen teaming up with Green Lantern and spends most of his personal time with the love of his life, Black Canary.

A seasoned actor who has had roles in edgy shows like Queer as Folk and Hung, Stephen Amell was relatively unknown when he was first cast as Oliver Queen/Green Arrow. However, he soon won fans over with his earnest portrayal of the haunted hero of Star City who struggles for redemption while keeping his city safe. While the storylines haven't always been able to allow this actor to shine, it is Amell's performance that is one of the main reasons people still watch the show after five seasons.

13 BAD: CHRIS WOOD AS MON-EL

The character of Mon-El has gone through various iterations in the comic books, but aside from joining the Legion of Super-Heroes and marrying Shadow Lass in the mid-'90s, he is basically a rip-off of Superboy right down to the same abilities. Creators of Supergirl thought it would be a good idea to bring this character into their universe during the show's second season as a love interest for Kara.

Prior to being cast as Mon-El, Wood is probably best known in his recurring role as The Vampire Dairies' season six villain Kai, an evil warlock. While he was strikingly cunning and mischievous as Kai, Wood's turn as the rogue-ish lady's man Mon-El just fell flat. Also, despite the fact that Wood and Supergirl's portrayer, Melissa Benoist, were dating in real life, fans complained that the chemistry just wasn't there on screen.

12 GOOD: CAITY LOTZ AS SARA LANCE/WHITE CANARY

While there have been several incarnations of Black Canary, they all have some things in common: fierce fighting styles, a sonic scream and a penchant for leather. Throughout Arrow's five years, there have been three Black Canaries all together, with each of the previous characters dying and passing the mantle on to another. It seems a bit of a running gag, and many viewers aren't fans of how the character has been treated.

However, one of the good things to come out of this is Caity Lotz's performance as Sara Lance, a character created just for Arrow. Her riveting and heartbreaking performance as The Canary during her time on Arrow was so popular, they spun her off into her own team-up show, Legends of Tomorrow. As one of the few bisexual characters currently on TV, Sara takes no prisoners and assumed the identity of White Canary following her resurrection.

11 BAD: CANDICE PATTON AS IRIS WEST

In her first appearance in the comic books, Iris West is an intrepid reporter for Central City's Picture News and is Barry Allen's fiancee. Her character would go on to be killed, resurrected and kidnapped like most humans in a relationship with superheroes. However, the most recent iteration of Iris has a much more aggressive and independent attitude, similar to the transformation Lois Lane has gone went through in recent years.

Candice Patton's previous acting gigs consist of various daytime dramas and a recurring role on The CW's The Game, and unfortunately, it shows. Her character often comes off as whiny, needy and patronizing, spending many episodes not having much of any character direction. This may be largely the writer's fault, but now that Iris has taken on a leadership role with Team Flash, maybe things will get better.

10 GOOD: EMILY BETT RICKARDS AS FELICITY SMOAK

Formerly a minor supporting character featured in The Fury of Firestorm as the manager of a computer software firm who eventually became the wife of Edward Raymond, Felicity Smoak was indeed a peculiar choice as a supporting character in a TV show about the Green Arrow. Following the success of the show, the character was reimagined in the New 52 to correspond with how the character is portrayed on the show.

Emily Bett Rickards was cast as Felicity Smoak in what was only meant to be a one-episode guest star stint in season one, but following positive reaction from her co-stars, Warner Brothers and viewers, she was upgraded to a series regular in season two and has been an integral part of Team Arrow ever since. Not bad for a girl who starred in a Nickelback video.

9 BAD: MEHCAD BROOKS AS JAMES OLSEN

James "Jimmy" Olsen is a classic Superman character who is a young photojournalist who works with Lois Lane and Clark Kent at the Daily Planet. Jimmy looks up to his coworkers as role models and parental figures, frequently working with them to break stories and fight crime. Jimmy has been featured in a variety of Superman-related projects, including the Christopher Reeve movies and The CW's Smallville.

For someone who has an extensive track record of acting on television, Mehcad Brooks' updated depiction of James Olsen feels flat and one-note. Fans have also stated he brings a bit of arrogance of the character they're not used to seeing. With regular roles on past hit shows like True Blood, Necessary Roughness and The Game, we expected more from Mr. Brooks.

8 GOOD: VICTOR GARBER AS MARTIN STEIN

In the comics, Martin Stein is a Nobel Prize-winning physicist and one-half of the duo who comes together to form the "nuclear man," Firestorm. While initially he doesn't get along with his high school student counterpart, Ronnie Raymond, the two eventually bond and come to learn a lot about life from each other while fighting the forces of evil. After the New 52, Martin is a professor who aids the new bearers of the Firestorm mantle, Ronnie Raymond and Jason Rusch.

Awarding-winning veteran actor Victor Garber was cast as Professor Martin Stein, initially in a few episodes of The Flash, but would later become a series regular on Legends of Tomorrow. Garber steals the scene almost every time he appears onscreen, elevating the performances of those around him. From Titanic to Alias, there's nothing this accomplished actor can't do.

7 BAD: KATIE CASSIDY AS BLACK CANARY

DC fans will know Black Canary as the tough-as-nails love of the Green Arrow's life, who also went on to be a founding member of the Justice Society of America and was a long-term member of the Justice League of America. A martial arts expert with a high-powered sonic scream, she is one of the fiercest fighters in DC history.

Considered a modern-day scream queen after turns in Black Christmas and A Nightmare on Elm Street, Katie Cassidy had her breakthrough in television when she was cast as Arrow's Laurel Lance in 2012. While she did fine playing Laurel as an attorney, it was when she took up the mantle of her dead sister's superhero identity, Black Canary, when the real problem started. The look of the new Black Canary was off-putting and Cassidy seem to be uncomfortable in the role, which showed.

6 GOOD: CALISTA FLOCKHART AS CAT GRANT

Cat Grant debuted as a gossip columnist for the Daily Planet in the late '80s, with intentions of her becoming a love interest for Clark Kent and a rival to Lois Lane. However, along with everyone else, her character was reset after the New 52, which softened her character and how she was portrayed. In DC Rebirth, her character is molded to mimic the Cat Grant from the Supergirl TV series.

Calista Flockhart is an award-winning actress best known for her work on Ally McBeal and Brothers and Sisters, so it came as a bit of a surprise that the actress was cast as the CEO of CatCo Worldwide Media and Kara's boss in Supergirl. Indeed her portrayal quickly became one of the best parts of the show. She quickly became a trusted confidant to Supergirl and mentor to Kara, making audiences fall for her even more.

5 BAD: GRANT GUSTIN AS THE FLASH

A stalwart DC comics superhero who has been around since the '40s, the Flash/Barry Allen is known for his super speed and humorous personality. While there have been a variety of speedsters running around the DC Universe, Barry Allen is who comes to mind as the real Flash, the one who's been depicted throughout the pages of the Justice League of America and has been developed into not one, but two, live action television shows.

Unlike John Wesley Shipp, the actor who played the Flash in the 1990 series, Grant Gustin completely misses the mark of being a lighthearted speedster who is trying to learn how to use his powers to help people. Gustin's performance has been all over the place, from being overly naive to the cockier, more self-centered Flash as of late. Gustin could take some cues from Shipp's performance by adding more depth to his character.

4 GOOD: JOHN BARROWMAN AS MALCOLM MERLYN

In the comic books, Malcolm Merlyn was first known as Merlyn the Magician, an archer who inspired Oliver Queen to become Green Arrow. However, Merlyn would later become a member of the League of Assassins, turning each other into archenemies. His villainous career would continue, becoming a member of the Injustice Gang and facing off against Young Justice.

Scottish-American actor and singer John Barrowman was a pop culture favorite long before taking on the role of Merlyn, after appearing in TV shows like Doctor Who and Torchwood. Originally starting out as one of the series' main antagonists, his character would eventually seek redemption after finding out that Thea Queen, Oliver's sister, is his daughter. The nuances Barrowman brought to his performance were some of the best of the series, it's a shame they seemingly killed him off at the end of season five. Here's hoping he finds another Lazarus Pit.

3 BAD: JOSH SEGARRA AS PROMETHEUS

Prometheus debuted as a villain of the Justice League of America in the late '90s and was a frequent member of the Injustice Gang. In the books, he is an intellectual genius, a martial arts expert and uses cybernetic implants to further augment his abilities. He is one of the few villains who has single-handedly came close to defeating all of the Justice League.

Josh Segarra has been acting for more than a decade, so when it came to light who Prometheus was on Arrow, we were hoping for just a bit more of a performance than what was delivered. As Adrian Chase he worked alongside Oliver Queen for the first half of the season, then it just went downhill from there. Chucking pretty much any link to the source material, this Prometheus seems meant to be The Joker to Green Arrow's Batman, leaving most of their interactions feeling forced.

2 GOOD: MELISSA BENOIST AS KARA ZOR-EL/SUPERGIRL

Usually depicted as Superman's cousin, Supergirl has been around since the late '50s and has been present for many major DC storylines. She was infamously killed off in 1985's Crisis on Infinite Earths and retconned out of existence, only to reappear almost 20 years later. She was even given the big screen treatment in 1984's Supergirl (even though it was a box office flop, it's still the first superhero film to feature a woman as the lead).

A relative acting newcomer with a strong music background, Melissa Benoist was cast as the lead in Supergirl in 2015 following the end of her series regular gig on Glee. Many viewers had their doubts about her pulling off such an iconic character, but Benoist won viewers and critics over with her genuine, optimistic and vulnerable portrayal of Kara. Now in season three, Supergirl and Benoist show no signs of stopping anytime.

1 BAD: CIARA RENEE AS HAWKGIRL

As one of DC's earliest superheroines, Hawkgirl has appeared in a fair amount of flagship team-up titles, including Justice League of America and Justice Society of America. There have been several incarnations of the character, but each Hawkgirl is depicted as being a fierce warrior who typically uses archaic weaponry and possesses a large set of wings to fly. While the character has been featured in multiple DC animated projects, we would not get our first live-action appearance until the Arrowverse debuted.

First appearing briefly in The Flash, Ciara Renee was cast as Kendra Saunders/Hawkgirl and was a series regular during the first season of Legends of Tomorrow. However, this Hawkgirl was extremely different from the character we had come to love over the years. Renee's portrayal of Hawkgirl fell prey to often being the damsel in distress and overly emotional, while her acting came off as stiff.

Which of these do you agree or disagree with? Let us know in the comments!