The annual convention can make (''Iron Man'') or break (''Stealth'') a film

In 1970, 300 comic-book fans convened in the basement of a dumpy San Diego hotel for the first Comic-Con. Conceived as a peaceful nerd Eden where fanboys could score a dusty back issue of The X-Men or an autograph from its co-creator Jack Kirby, the annual four-day convention was so far under Hollywood’s radar that the only ”stars” who showed up in those early years were Frank Capra and Chuck Norris.

But in the last decade, Comic-Con has exploded into the most important pop culture event on Hollywood’s calendar — a frenzied marketing free-for-all where, each July, major studios and networks flaunt their coolest new projects, trying to woo an audience of 125,000 sci-fi, fantasy, and horror fans. ”It’s like Sundance for nerds,” says film director John Erick Dowdle (The Dry Spell). Only far riskier. Crowd reaction at Comic-Con can rocket a film to riches (Iron Man) or kill it in its cradle (Stealth). ”It’s scary,” says X-Men franchise producer Lauren Shuler Donner. ”If they don’t like the preview of a movie, [that reaction] is going online.”

Hollywood wouldn’t be at Comic-Con at all if it weren’t for the Internet. Harry Knowles of Ain’t It Cool News and other bloggers burst onto the scene in the mid-’90s, reaching millions. Hollywood needed to cater to them, fast. Comic-Con was the answer. ”It’s mutual exploitation,” says producer Gale Anne Hurd (The Terminator). Sure, but no one doubts that the fans are the ones in the driver’s seat. ”You get the feeling,” says comic-book writer Brian Michael Bendis (Torso), ”that Hollywood is afraid not to come.”