SAN DIEGO, Calif. -- Some battles can't be won. But like the 300 Spartans in his last film, Zack Snyder isn't budging.

At issue? The three-hour length and adult content of his adaptation of Watchmen, the 1986 graphic novel that broke new creative ground with its violent, dense, psycho-sexual reinvention of the superhero genre.

Although the movie doesn't hit screens until March, it is already one of the most anticipated films of 2009 -- as evidenced by the thunderous applause Snyder received at this weekend's Comic-Con.

All along the 42-year-old director, who traded on his post-300 clout to get the movie made, has been faced with pleasing two constituencies: the tome's rabid followers who don't want the story tampered with and studio executives who expect a sure-fire blockbuster.

"I can only cut out so much before it stops being Watchmen," he told journalists, "and I'm not going to do that."

Filmed in Vancouver last year, the adaptation stars Malin Akerman, Jackie Earle Haley, Patrick Wilson, Matthew Goode, Jeffrey Dean Morgan, Carla Gugino and Billy Crudup as disgraced, dysfunctional superheroes in an alternate-history 1980s America where Richard Nixon is still president and costumed vigilantes are outlawed.

Crudup, who portrays the luminescent god-like Dr. Manhattan thanks to some startling motion-capture CGI, had never read the book and was "shocked by the script, frankly. I didn't know the book. I just got the short brief from my agent, that it was based on a graphic novel so I came with my ideas about what it would be like. Scripts I've read about graphic novels -- many of them have the same characteristics, which is the thing we love about comic book movies. They set up the expectations and fulfill them. So to read this script that subverts those expectations at every turn to me was solid."

Interestingly by the mid-1980s, comics themselves had grown stagnant and cliched and were revitalized by two crucial works: Frank Miller's The Dark Knight Returns -- clearly a critical influence on the current Batman sequel -- and Watchmen.

Likewise, Snyder believes the comic-book movie boom of the past few years only "primes the pump" for his subversive epic. "It's a huge help... The more superhero movies you get, the better, because it makes the mythology within the culture all the stronger. Then when you take the mythology apart, people understand it."