Welcome to Comic-Con, where Stan Lee is God and Dan Martin finds that you're nobody without a good get-up

Back in 2005, top aspirational celebutard drama serial Entourage featured an episode wherein Vince and the boys drove out to San Diego for Comic-Con; the four-day superhero love-in where California gets its geek on and Stan Lee is the One True God. The joke was that this was the only place on Earth that Vince's less-successful older brother Johnny Drama - having starred in a bizarre low-budget Xena-style schlock series in the 1980s - was the bigger star. Here was a parallel universe where the geeks really had inherited the earth.

Last weekend, the whole shebang roared into action once more, taking over California's cultural consciousness in a sprawl of graphic novels, steampunks, Tamagotchis, time-travellers, Terminators, and more people dressed as The Joker than the combined forces of the DC Universe of superheroes could ever hope to see off. With 150,000 people spread over the six square miles of San Diego Convention Centre, this is the Sundance of geekdom, a place where a working knowledge of the moons of Alderaan will actually help your chances of getting laid.

The place might be crawling with megastars (safely protected from the more devotional of their disciples, of course), but the real stars here are the fans. Devotees of the superhero dress-up cult known as "cosplay", they make the pilgrimage from all over the world.

People like Bob Mitsch, the Pasadena Doctor Who fan who's marshalled an army of 10 likeminds to parade around in perfect replica costumes of Doctors one through 10.

Or the teenagers camped outside the Convention Centre terrace. There's a twofold advantage here: they'll hardly get cold in the 40-degree heat, and sleeping outside the 6,000-capacity hub that is Hall H is the only sure guarantee of getting a seat at the coveted Heroes session, where the entire cast will unveil footage from Chapter 3, Villains, and be quizzed by their fans.

Or people like Dan Enfield, a 39-year-old computer programmer who's come dressed as Red Arrow, gleeful that he gets to be a celebrity for the day. "Growing up I loved comic books, a lot of people did," he says. "But I think we were afraid to express how we felt and, y'know, kept ourselves to this other world. Here you're not alone. Everybody shares your dream."

In the overwhelming vastness of the exhibition hall everything from The Clone Wars to Emily The Strange to Knight Rider to BBC America to Dark Horse Comics to My Little Pony has a presence, selling, showcasing or just hanging giant fibreglass effigies of their characters from the ceiling. Giant Pokemon look down on animatronic Hulks, Ghostbusters squadrons from every state in America parade the hall in search of ectoplasmic menace. And there are even more Jokers. Amid it all sits John Barrowman, putting in eight-hour signing stints behind a notice that roars "NO FLESH WILL BE SIGNED!"

"Oh, the reason for that?" bellows Barrowman when quizzed. "People want you to sign their skin, but you don't know if they have an allergy to the ink."

John's here to plug his role as Captain Jack (and play down his expected casting in Marvel's Captain America movie); Torchwood is BBC America's highest-rated show ever, a far bigger deal in the US than Doctor Who. So John, Naoko Mori (Toshiko) and Gareth David-Lloyd (Ianto) are over to meet their public. Hardly a shrinking violet, even Barrowman is overwhelmed. "I describe it to people as like the Cannes Film Festival but for science fiction. I'm a nerd myself so I enjoy this kind of stuff."

The truth, though, is that in the three years since that episode of Entourage aired, that parallel universe has shifted to the point where we all now occupy it. With the music industry in freefall and conventional celebrity lost in snideness, the cult world is fast becoming entertainment's biggest business. Only Sex And The City made more noise this summer than the big three superhero movies. A culture built upon heroism can't be sullied by incriminating YouTube clips or DUIs. Geeks did inherit the Earth, and now everybody else wants a piece. In one night here you'll run into Samuel L Jackson, Keanu Reeves, Mark Wahlberg, Mark Hamill and Mel B.

"There are girls everywhere. Normally, straight up, this place used to be full of guys," says Seth MacFarlane, the brains behind Family Guy. "It's a whole new Comic-Con. It's like a frickin' Coldplay concert, girls whooping the whole time!"

But it's not the actors who are truly revered here, but the creators. People like Joss Whedon, who's here to preview his new series Dollhouse with the rather ace Eliza Dushku. The show won't air until 2009, but fans are already fielding online petitions to prevent its cancellation, after his last show Firefly was taken off air mid-season. "The enthusiasm of it I adore," shrugs Whedon. "And the wariness? Well, it's earned."

Or Frank Miller, here to preview his solo directorial debut, an adaptation of the comic pioneer Will Eisner's strip, The Spirit, starring Samuel L Jackson and Scarlett Johansson. Or Simon Pegg, Jessica Hynes and Edgar Wright, returning to America victorious after seeing off the botched plan to remake Spaced US and met by a queue that stretches right outside. Or Kevin Smith, who is everywhere ; hosting the Battlestar Galactica session ("A show so good it will get you pregnant") and unveiling his new movie Zack And Miri Make A Porno with Seth Rogen, Elizabeth Banks and Traci Lords in tow.

But most of all, it's about Marvel overlord Stan Lee. "A few years ago I experienced a bad time in my life and I thought about ending it all," confesses one unfortunate fan at his panel session. "And the reason I didn't, Stan, was you and your comics. I experience rage like the Hulk. I get confused about my identity like the X-Men. Now I live for two things: Stab - my six-year-old boy - and your comics."

The jewel in the crown are Friday night's prestigious Eisner Awards, the industry's Oscars. This year's surprise winner, was My Chemical Romance singer Gerard Way's dysfunctional superhero saga The Umbrella Academy, picking up Best Limited Series for its first run - a sweet vindication after more than a few eyebrows were raised when he started the project with illustrator Gabriel Ba.

"A lot of people were probably thinking, 'He's not much of an underdog any more, he's a rock star now so this is easy for him,'" says Gerard. "So I got to be an underdog all over again. I didn't have it easy."

Deified in his day job, Gerard used to be able to walk around these things pretty much invisible. Now, all that's changed.

"At first I would just go to comic conventions and just walk around. Now I make that difficult for myself because I write comics. But it's so good to have a book that was appreciated. Acceptance was optional, I wanted the work to be appreciated."

A final thought from our new friends Matt and Ramona from Temecula, CA, who rounded off our Comic-Con by solving its final mystery - the difference between a geek and a nerd. "A geek is somebody who bites the heads off chickens in a circus. A Nerd is just way cooler."

The best of Comic-Con

The Spirit

Sam Jackson and Scarlett Johansson camp it up in comic legend Frank Miller's big screen adaptation of Will Eisner's classic strip. Out in January.

The Cleveland Show

Family Guy spinoff billed as a "black Brady Bunch". Cleveland moves back to Stool Bin, Virginia, marries childhood sweetheart, lives opposite a redneck couple and a family of bears.

Dollhouse

Buffy man Joss Whedon's new Eliza Dushku vehicle. She plays Echo, one of a "Dollhouse" of government agents whose memories are wiped after each assignment. BSG's Tahmoh Penikett co-stars.

Caprica

Planet-bound prequel to BSG, a "sci-fi Dallas" that charts the development of the AI technology that would become the Cylons. Eric Stoltz stars.

Ghostbusters the video game

The ENTIRE ORIGINAL CAST are back to do the voices for what is effectively Ghostbusters 3 - it's set right after the events of the first movie; Dan Aykroyd and Harold Ramis wrote the script.

Mortal Kombat VS DC Universe

Supes, Batman and Catwoman beat living crap out of the MK characters; though strict licences won't let them actually kill in what developers hope will be the first MK game to get a teen rating.

Zack and Miri make a Porno

Seth Rogen and Elizabeth Banks fall in love making amateur rudey film in what's hopefully Kevin Smith's return to form. Your actual Traci Lords is in it, too!

Watchmen

Zack Snyder's 2009 follow-up to 300 adapts DC's brutal series about vigilante warriors in the 1980s.