But after a splashy premiere at the 2011 geek-fest in San Diego, the film—which featured Harrison Ford as a cattleman who tries a save a town from aliens—landed with a thud when it opened nationwide. Critics bashed its quirky blend of western and sci-fi and it brought in a paltry $100 million—just enough to cover its bills.

There’s a lesson here: Despite the promise of legions of fans, eager to spread the word about new movies and TV shows, a big showing a Comic-Con, the annual four-day geek-fest that began Thursday in downtown San Diego, doesn’t guarantee a hit.

“A good presentation is no substitute for a bad film,” says David Glanzer, Comic-Con’s international director of marketing and PR. “Having a presentation can create positive word of mouth to other early adopters and those who tend to see movies on opening day. However, it is also important to recognize that a killer presentation of a few minutes of a new film may generate huge applause and buzz, but if the film doesn’t in the end, our fans will stay away.”

A similar fate befell Scott Pilgrim vs. the World, another Universal movie, which premiered at the Con in 2010. Given its roots as a graphic novel, the flick featuring Michael Cera as a musician who battles his ex-girlfriend’s murderous beaus seemed custom tailored for the Comic-Con crowd. The studio even dropped north of $200,000 to wrap one of the Hilton Bayfront towers with a massive Scott Pilgrim poster. The movie also premiered there.

But the good buzz started and stopped at the San Diego Bayfront: Though critics generally dug the story, the movie only made a reported $31 million.

Still, cases like Scott Pilgrim are the exception rather than the rule, argues Glanzer. “I think every studio hopes for a blockbuster and Comic-Con can be a great barometer of a project being on the right track. But a lot can happen between a presentation in Hall H and a film’s release a year later. I think studios continue to return to Comic-Con because it is a great way to hear from the end user. They hear the questions asked, judge whether something works or not in the presentation and then can make of that information what they will.”

The trick is to figure out the most effective way to get their message heard. Given the massive surge of TV shows that have taken over the Con, it’s harder than ever to capture the attention of the 130,000-plus fans who will converge upon this weekend’s sold-out event. Some studios still think the only way to do it is by going big: TNT installed a massive building wrap at the Marriott for its new drama The Last Ship, while FX papered one side of the Hilton Bayfront with a creepy poster promoting its Guillermo Del Toro drama The Strain.

In stark contrast, HBO only hung a few Game of Thrones banners alongside the downtown trolley tracks—but then, the drama that just wrapped an exhilarating fifth season and hardly needs to struggle for eyeballs. The show’s Friday panel in Hall H featuring Gwendoline Christie (Brienne of Tarth), Natalie Dormer (Margaery Tyrell) and Conleth Hill (Varys), among others, is one of the most sought-after tickets at the Con.

In fact, it’s during those panel discussions that the studios have the best chance at reaching their target audience. That’s why Disney doesn’t have to invest in gigantic building wraps to promote Star Wars: The Force Awakens, which is set for release in December. All is has to do is promise a visit from director JJ Abrams and a “special look” at the prequel and it can safely assume that the 6,500-seat Hall H will fill to capacity.

On a smaller scale, studios have found that screening the first episodes of upcoming TV shows can be an effective promo tool. This year, Warner Bros. showed the new CBS drama Supergirl and Syfy decided to unveil the first episode of The Expanse, ­months before either show is scheduled to debut.

“The more we can surprise them and spark their curiosity, the more they respond,” says Sara Moscowitz, SyFy’s senior VP of brand and strategic marketing. “We often don’t know what we’ll be up against. It’s like going into battle in some ways,” she says. “How can we up our game for a group of people who welcome that? But that’s the fun of it.”