Sequels are not destined to be rubbish - they aren’t subject to the apparently inexorable laws making most remakes terrible. After 2 Fast 2 Furious and all that pap last year, Spider-Man 2 - like Shrek 2 the week before - has wowed many observers. Not only does it appeal to the ’kidult’ demographic by packing in parents, their kids and independent teenagers, it also delivers by entertaining them all intelligently, without resorting to grafting adult gags on to the kids’ action scenes (anyone for The Cat in the Hat?).

Spider-Man 2’s other great marketing trick is to reinvent a version of an existing character while keeping the original fans on board. There are sufficient regular readers (’fanboys’) to support several monthly Spider-Man comics, but not necessarily enough to make a multimillion-dollar feature film (or film franchise) profitable. Television shows can limp around in a DVD and convention afterlife by drawing on the fanbase. But once you start costcutting on comic-book adaptations they look awful. (Anyone fancy watching Superman IV: The Quest for Peace tonight? Didn’t think so.)

The rise of computer-generated imagery (CGI) has meant that many superhero projects discussed in the 1970s and 80s are now more achievable, but bad CGI is no better than cheap special effects. And even without cost issues to consider, nothing can help a chronic script (step forward, Batman and Robin).

Taking the long view, it’s apparent that superhero movies, despite the occasional blockbuster, have been essentially a minority sport. The late ’70s/early ’80s success of the first three Superman films did little to undermine the way that for mainstream audiences, the figure of the superhero was always tainted by the camp Batman TV show and its big-screen spin-off. The Incredible Hulk and, to a lesser extent, Spider-Man could thrive on 1970s TV provided they faced off against everyday criminals (and ninjas) and avoided wheeling on the costumed villains.

But elsewhere, characters from Marvel and DC comics seldom ventured off the four-colour page, except into cartoons. As live action it was all too silly after the age of seven, especially Batman. In his essay "Batman, Deviance and Camp," cultural critic Andy Medhurst recalls "pure pleasure, except for the annoying fact that my parents didn’t seem to appreciate the thrills on offer. Worse than that, they actually laughed. How could anyone laugh when the Dynamic Duo were about to be turned into Frostie Freezies?"

If Medhurst later came to "share that once infuriating parental hilarity" (at least until he wrote the essay that partially rehabilitated the character), then so too did mass audiences most of the time. Charting the discussion of comic characters as entertainment in the 15 to 20 years since I was an intern at the Final Frontier comic shop, it’s striking just how defensive the industry has been. Contriving the term "graphic novel" instead of "comic," rather than claiming to be art or literature, and the distancing of a successful movie like Blade from its comic book origins - it all adds up to a part of the entertainment industry being in denial. Meanwhile, the fanboys themselves acquired a reputation for poor personal hygiene and needing to get out more, embodied in "Comic Book Guy" off The Simpsons.

In defense of the comic, it is worth pointing to its ability - not unlike other forms of entertainment - to connect with wider social changes. Indeed, some overestimate the influence of comics to make a case for a red thread of immigrant radicalism in mass entertainment. While Superman evolved into a patriotic symbol, his fantastic origins owed much to immigrant fantasies of transcendence. Kill Bill Vol 2 sees Bill (David Carradine) remind us that Clark Kent is only Kal-El’s disguise, but for creators Jerry Siegel and Joe Shuster, Superman was a steely alternative to being a bespectacled mensch.

DC Comics was in turn overtaken by Marvel Comics in the 1960s, precisely because the Marvel characters had flawed private lives echoing those of their college freshman readers, which later on connected to the nascent counterculture. Marvel stories were set in Manhattan rather than "Gotham City." Apart from a classic run on Green Lantern, DC had no reply to the "realism" of X-Men, Fantastic Four and Peter Parker as "old webhead himself."

The Spider-Man comic appealed to its fanbase almost as consistently as its hyphen was used inconsistently. Spider-Man director Sam Raimi plays to his own fanbase too, hence cameos from Bruce Campbell, his brother Ted Raimi and the car used in his feature debut The Evil Dead. (This has also got my fellow video-nasty buffs gloating, a quarter century after Raimi’s "Ultimate Experience in Gruelling Horror" was banned in Britain.)

And sure enough Spider-Man 2 is a treat, with Parker struggling with the decisions made at the end of the last movie and Alfred Molina putting in a gothic performance and changing from a humane scientist to one infected with sinister AI nanobots, rather than simply mad. (Occasionally his "Doctor Octopus" arms move like Rod Hull’s Emu, but that’s still pretty sinister.)

A number of commentators have scrabbled around for answers as to why we like our heroes flawed these days. "When did men in tights discover the courage to bare their soul?" asks Sean Macaulay in The Times (London). One answer is that since comic characters are empty vessels, despite the layers of mythology built up behind them over the years (origins, alternate realities, parallel universes, crossovers - ask a fanboy), they can play more or less any role we want them to.

Marvel’s 1940s Nazi, the Red Skull, resurfaced as a communist in the 1960s, while his opponent Captain America spent the late 1980s espousing a moderate form of patriotism. DC’s Dark Knight Returns version of Batman - instrumental to Tim Burton’s 1989 film adaptation of the character - battled an urban underclass, while Superman became a CIA stooge in Frank Miller’s comic, and via a handsome romantic lead on prime-time TV opposite Teri Hatcher, he is now a confused teen on Smallville.

Although he has been troubled since his first appearance in Amazing Fantasy #15 (1962), Peter Parker is also a figure for our times. Thus his superpowers derive from a genetically modified spider as opposed to the comic’s radioactive version. And who better to inspire kids in a counselling culture than a hero who himself needs counselling (and gets his "dreams" of being Spider-man analysed in the course of the movie)?

After all, many of the more conventional fictional heroes have lost their luster. When was the last time you saw a cop or espionage thriller where the protagonist wasn’t betrayed by his superiors? Anti-terrorist movies might go in for ethnic stereotypes from time to time, but generally the first set of villains turn out to be wheels within wheels, backed up by US agency chiefs (see 24 and Alias for endless double-crosses, betrayals and double double agents).

In contrast, the superhero seems untainted in comparison to the "real heroes" of 1980s cinema. Throw in enough CGI to make things look decent, build on the "pre-sold" characters in Marvel and DC copyright (including merchandising opportunities), keep the fanboys away from the test screenings, and you have a formula for success. It is fitting that Mary Jane Watson (Kirsten Dunst) ends up with the troubled nerd rather than astronaut John Jameson (Daniel Gillies), given that the former is a hero for our times.