When you see the happy hordes at Comic-Con, the parade of fanboys and fangirls dressed as Vulcans and superheroes and warrior princesses and Hobbits and zombies, it’s easy, at first, to think that what’s going on is all too quaint, fun, whimsical, and childlike. Yes, it’s very much all of those things. But it’s also more: fans elevating what it means to be a fan into something nearly metaphysical. What Comic-Con reveals is that America — with, perhaps, the rest of the world not too far behind — is becoming a land of avatars, of people who long to make themselves into their favorite characters because it somehow completes them. It fills in who they are. And no film since “Trekkies” reveals the soul behind that impulse with quite the cracked exuberance of “Ghostheads.”

It’s just a little documentary, currently showing on Netflix, about all the people who’ve turned “Ghostbusters” into a religion. There’s a “Ghostbusters” chapter in every state, and tellingly, each one of these organizations refers to itself not as a “club” but as a “franchise.” They’re thinking just like the folks who make the blockbusters. What’s friendly, and funny, and appealing, and revealing about the “Ghostbusters” fan brigade is that if you contrast them with, say, the fans of “The Lord of the Rings” or “Batman,” there’s an undeniable dark drama to the last two. People take their Tolkien deadly seriously, and if your overwhelming drive in life is to dress up like a caped crusader, imagining yourself as a noble avenger in the night — well, that’s Bruce Wayne’s drive as well. The very obsessiveness of fan worship mirrors his own splintered search for identity.

But to become a Ghostbuster? That’s a far more benign and seemingly unobsessive endeavor. Here’s what it involves: You fashion yourself one of those khaki cosmonaut/exterminator suits embellished with your own name in place of Venkman or Spengler. You build yourself a proton pack — a relatively elaborate piece of construction that involves getting all the lights and nodules in the right place, though these days you can also just purchase a proton pack for $54.95 at Wal-Mart. And…that’s it! You’re a Ghostbuster now. You sit around with your fellow Ghostbusters talking about “Ghostbusters” or posing in groups of three or four, energy weapons at the ready, looking like you’re on the way to a ghost-bust. (You also show up for a lot of charity work; the Ghostbusters are nothing if not generous.)

As “Ghostheads” reveals, there are people throughout America who long for nothing so much as to live inside the family of “Ghostbusters.” All of which raises the question: Why? What is it about “Ghostbusters”? Why is it anything more than a fondly remembered special-effects comedy jam from the ’80s? Why is it a myth, a cult, a womb of hilarity people long to return to?

The answer, ironically, has to do with everything that’s ramshackle and throwaway and, in all likelihood, un-reproduce-able about it. To watch “Ghostbusters” today is to be immersed in the attitude of the ’80s, a deeply cozy innocent snark that mirrors the attitude of everyone watching the movie. It’s a vibe embodied — uniquely — in the presence of Bill Murray, who may have been alone in realizing that he wasn’t simply starring in a comedy about a team of scientists out to defeat an epidemic of ectoplasmic activity. He was starring in that movie and standing outside it at the same time. He was starring in his own private Marx Brothers picture, a winking nattering nudgefest that only pretended to be a comedy about a team of scientists, etc.

Confronting that snarling she-demon on the roof who looks like Sheena Easton in a bad video, Murray says, “All right, this chick is toast!” The way “Ghostbusters” works is that that line reduces her — and the whole movie — to toast before any weapon is fired. Murray’s theater-of-the-absurd nonchalance turns “Ghostbusters” into the Mad magazine parody of itself. He was the star, but he was also part of the audience, effectively sitting on the couch along with the rest of us, watching himself. After more than 30 years, that’s what still draws people to “Ghostbusters” as if it was their very own. Murray stood outside the frame much more than he did in a movie like, say, “Stripes” (for my money, his most uproarious film). And he could do it because “Ghostbusters,” funny as it is, is such a proudly goofy cheeseball farce-lollapalooza. Murray’s “Hey, relax, it’s only a movie” vibe was the pipeline connecting him to the audience and the audience to the movie.

The makers of the new “Ghostbusters” were under no obligation to mirror every detail of the original; if anything, they may have been almost too loyal. And Internet hate aside, the decision to flip the gender of the lead characters was an inspired one. But to truly re-conjure the spirit of “Ghostbusters,” what the remake needed was some equivalent of the Murray ‘tude. Kristen Wiig, a postmodern comic virtuoso herself, certainly seemed an ideal candidate to do that. But Wiig, as the defrocked academic Erin Gilbert, is less arrogant than abashed; she’s folded into the story and isn’t allowed to wink at its lunacy. And maybe that’s because Wiig and her costars, along with director Paul Feig, have made a perfectly decent comedy that’s trying so gamely to treat it all with reverence that they lost sight of what made the original “Ghostbusters” special in the first place — its ticky-tacky irreverence, with Murray’s witty meta insolence practically poking a hole in the sets. That’s what viewers are nostalgic for: a time when not caring that much was something to giggle at.