Comic-book movies are a big focus at Comic-Con (search) these days, with another one, "The Fantastic Four," just crossing the $100 million mark.

But the movie that had everyone buzzing at this year's comic convention was "Superman Returns," (search) the highly anticipated film from "X-Men" director Bryan Singer scheduled to hit theaters next June.

Warner Bros. even flew Singer in from the "Superman" set in Australia so he could show some exclusive footage to Comic-Con attendees — a strategy, according to Hollywood literary manager Jonathan Hung, that is getting more and more popular with studios.

As Hung put it, Comic-Con has become the most effective test-screening for studio comic-book movies. If they don't get a favorable response from the core audience, "they will change the direction they are going with the movie," Hung said.

"Variety did a huge article about how 'Catwoman' and 'Electra' got booed there," he added.

Apparently it was too late to save either of those movies.

But when you're dealing with a fan base as touchy as comic-book die-hards, why do studios even bother with superhero movies?

Two words: franchise potential. A built-in return audience is every studio's dream.

"These movies are so related to the core audience [and they] will come to see it two, three, four times," Hung said.

Sure, summer and holiday moviegoers keep the numbers going, "but it's these 'kids' who can make or break these movies."

Other upcoming comic-book movies that were getting the geeks going at Comic-Con: Warner Brothers' "V for Vendetta," (search) starring Natalie Portman and set to come out in November; Columbia and Dimension Films' "Ghost Rider," (search) starring Nicolas Cage; and of course "X-Men 3" (search), slated for May of next year.

"My mother loved Wolverine," said Noah Meyers, an "X-Men" disciple hanging out at 2005's 36th Annual Comic-Con's Marvel booth. "'X-2' was even cooler; 'X-3' better be good."

Fans were also already getting pumped for the follow-up to the geek-approved "Batman Begins."

"I loved 'Batman Begins,'" said Jerry Bennington of Upper Deck Entertainment, a company that creates card games for head-to-head superhero battles. "I'm a huge 'Batman' fan, so I'm probably biased anyway, but I was so excited. I can't wait for the next one, 'cause the next one's going to be even better."

Dark Horse comics, the publisher of "Sin City," has had quite a bit of success adapting its own comic books — enough that it formed an entire division called Dark Horse Entertainment.

Some of its titles, "The Mask," "Alien vs. Predator" and "Hellboy," have made Dark Horse a serious contender in the world of comic-book films.

"We just optioned 'P.S. 238,' (search) a comic by Aaron Williams about a public school for the children of superheroes," said Chris Tongue, creative executive for Dark Horse Entertainment.

That's a concept not entirely unlike those of two upcoming superhero films: Disney's "Sky High," (search) (in a world where superheroes are just another part of society, how does a 13-year-old superboy cope with adolescence?) starring Kurt Russell; and Sony's 2006 release "Zoom," (search) starring Tim Allen (in a world where superheroes are just another part of society, how does a former superhero cope with obsolescence?)

"We're aware that there are a lot of other projects like this out there," said Tongue, "but this one has more heart and more brains than all of those put together."

Aside from comic-book movies adapted directly from comic books, you have a whole separate genre of movies that pay homage to comic books.

In director Ivan Reitman's "Super X," (search) Luke Wilson breaks up with Uma Thurman, who he thought was just a normal, everyday girl who would become a normal everyday ex. Turns out, she's a superhero who decides to use all of her superhero powers to get him back.

Wow, now that's wish-fulfillment for geeks.

Also generating excitement at Comic-Con: "Aeon Flux" (search), the movie — adapted from a short-lived series on MTV's "Liquid Television" — due out this fall starring Charlize Theron as an assassin after the head of a corrupt future government.

Theron even appeared at Comic-Con to promote the movie; the booth was so mobbed that this reporter couldn't even get through to get a free T-shirt.

But the movies are not what keep the geeks coming back to Comic-Con. Sure, the flicks are cool, but for the true comic book fans, they're just part of the experience.