Like a hot claw through butter, The Wolverine slashes its way into thousands of movie theaters this Friday. The latest installment in the increasingly sprawling X-Men film franchise sees Hugh Jackman reprise his role as the adamantium-laced antihero for the sixth time — and seeks to right the wrongs of his odious last spin-off, 2009's X-Men Origins: Wolverine.

And how, exactly, does The Wolverine plan to right those wrongs? By offering a grimmer, grittier take on a character that first appeared in Bryan Singer's relatively family-friendly X-Men back in 2000.

All dimly lit backdrops, brooding introspection, and visceral action, The Wolverine is the film fans have longed for since the character first clawed his way onto screens more than a decade ago. The new film is an adaptation of Chris Claremont and Frank Miller's 1982 comic-book origin story, which many hold up as the character's defining run.

But while this new film may give hardcore X-Fans what they want, it's also part of an unsettlingly large wave of brooding comic-book blockbusters. If you need evidence of the industry's obsession with self-serious superheroes, look no further than your nearest multiplex: The summer season has already served up Zack Snyder's joyless Man of Steel and the surprisingly introspective Iron Man 3. There's more of the same on the horizon: Marvel's upcoming Thor sequel will take its audience into a "dark world," and the sophomore outing for Captain America has been described by Marvel's Kevin Feige as "a '70s political thriller masquerading as a big superhero movie."

The latest swath of superhero movies is a far cry from the altogether more upbeat escapades that were enjoyed by Tobey Maguire in 2002's Spider-Man or the colorful heroes of 2000's X-Men — record-breaking films that helped blaze the trail for today's explosion of comic book adaptations on the silver screen.

So, to borrow a phrase from one of the genre's darkest figures: Why so serious, superhero movies?

After all, these characters are plucked from a medium known for its escapism. And let's be honest: These heroes are cape-wearing aliens, armor-clad millionaires, and Norse gods. It's okay to take ridiculously conceived superheroes seriously — but in the rush to be taken seriously, superhero movies have largely forgotten how to have fun.

In many ways, the darkening of the superhero genre reflects the trajectory that comic books followed more than 30 years ago. 1986 was something of a watershed for the comic book industry — a year that is widely credited as ushering in "The Dark Age" of comics with the publication of acclaimed series like Alan Moore's Watchmen and Frank Miller's The Dark Knight Returns. Suddenly, comic books were infused with darker political, psychological, and sociological undertones. Superheroes were no longer whiz-bang do-gooders who delighted kids, but anti-heroes with the same emotional baggage as the aging fans who read about them. As the subject matter moved away from the black-and-white morality that dominated the genre's so-called Golden Age, it delved into the shades of gray that lie between right and wrong.

So when did big-screen superheroes start to emulate their comic-book counterparts? Hollywood's treatment of superheroes experienced a similar transformation when Christopher Nolan's The Dark Knight hit theaters in 2008. Heath Ledger won a posthumous Oscar for his terrifying turn as the Joker, and the movie's failure to earn a Best Picture nomination has been widely credited with motivating the Academy to expand the field of nominees from five films to a maximum of 10.

Does the success of dark superhero films mean audiences no longer want superheroes to smile? How, for example, would modern moviegoers react to a whimsical, romantic Superman movie like the Christopher Reeve-starring Superman if it showed up in theaters today? For a likely answer, look no further than Brandon Routh, who did a pretty decent Reeve impression in 2006's Golden Age-inspired Superman Returns, which was tepidly received by critics and audiences alike. It's not for nothing that Man of Steel eschews the series' cinematic tradition in favor of emulating the tone of The Dark Knight. It's no longer enough for Superman to save the world; instead, he needs to spend his screen time contemplating his place in it.

There are a few heartening exceptions — Joss Whedon's relatively upbeat The Avengers springs to mind, as does the failed attempted to mount a superhero comedy with The Green Hornet — but in the mad rush for gritty realism, superhero movies are also running the risk of losing a little piece of their soul: The sense of whimsy and unabashed escapism that has attracted audiences of all ages through the years. Superhero movies, like action movies and romantic comedies, have become a genre unto themselves, and there's no reason that one movie — however effective — should set the tone for all the rest.