It's been nine long years since the first Anchorman film . But now the big-haired newscasters are back . What took them so long?

Tucked away on YouTube is a seven-minute tribute that purports to show the American Film Institute announcing Anchorman: The Legend of Ron Burgundy as the greatest movie ever made. Martin Scorsese, Dustin Hoffman, Steven Spielberg and Cher are wheeled out to wax lyrical about the picture's truth and humanity, periodically struggling with their emotions and welling up on camera. From here we cut to a shot of Will Ferrell pushing a man over in the street and Paul Rudd parading about the office liberally doused in rank aftershave. "Ugh," gags a colleague. "It smells like Bigfoot's dick."

How sad to report that this film is a spoof. What the editors have done is take lofty eulogies to the likes of Citizen Kane and La Grande Illusion and stitched them around a dopey comedy – and therein lies the humour. It's a nice idea, neatly executed. But hold your sides and catch your breath, because just who are we meant to be laughing at here? I used to assume the joke was on Anchorman. Now, I think it might be at the expense of the critics.

Anchorman: The Legend of Ron Burgundy followed the fortunes of a bunch of bumbling newsreaders in 1970s San Diego. It was directed by Adam McKay, produced by Judd Apatow and provided a revue-style platform for the rising "frat-pack" generation of American comics (Will Ferrell and Steve Carrell, Seth Rogen and Ben Stiller). When Apatow's film hit cinemas back in July 2004, it met with indulgent reviews and respectable box office. It was seen as mildly funny, a bit of amiable fluff. But then lowly Ron Burgundy took on a life of his own.

Next month sees the release of Anchorman 2: The Legend Continues, while the trailer shows the old gang reunited and shunted into an 80s era of green screen, political correctness and the 24-hour news cycle. The sequel comes buttressed by a mammoth marketing campaign that has involved Ferrell fronting a series of commercials for a luxury car and the launch of a limited-edition Ben and Jerry ice-cream entitled Ron Burgundy's Scotchy Scotch Scotch.

Admittedly, Anchorman's marketing sticks like a leech to the established Hollywood model. But its return is prompted by something altogether more noble: the slow-burn of fan love and a potential audience that has only grown in the intervening decade. Since its initial release, the original film has inspired club nights, fan conventions and a learned New York panel discussion that framed Apatow's profane, pratfalling caper (presumably semi-seriously) as "an important turning point in contemporary cinema". Even an AFI tribute does not seem so laughable now.

This giddying turnabout has caught the experts flat-footed. Most obviously, I think, it highlights a worrying snobbery within the critical community; a tendency to regard comedy as an inherently inferior genre; a cheap diversion not built for posterity. And yet happily it appears to have flummoxed the industry as well. In the past, Will Ferrell has admitted that preening Ron Burgundy, with his bristling moustache and overweening self-regard, was his all-time favourite role. All the same, he implied that the cast had now moved on to bigger, better things and were therefore unable to coordinate their schedules and reprise their old mischief. Moreover, in a recent interview with Salon, Adam McKay admitted that Paramount refused to green-light the sequel on three separate occasions before it finally saw the light.

If good comedy relies on timing, what are we to make of the nine-year lag between Anchorman movies? It may be unorthodox, but it sounds about right. Jump in too early and you wind up with a redundant cash-in like The Hangover 2 or a rash of interchangeable Police Academy flicks. Leave it too late and the joke goes stone-cold (as was the case with The Odd Couple 2, cobbled together three decades after the original and all but dead on arrival). And yet Anchorman 2 is that rarest of beasts. It's a Hollywood sequel that appears to have been allowed to develop organically, prompted by a growing whisper of public demand. With every passing year, the joke has become funnier and the fanbase more ardent. Yes, of course, the finished sequel might trample the dream and ruin the magic. But possibly not. If anything, McKay argues, the retro world of Ron Burgundy is the one we're living in now. "Sadly, he says, "the character has gotten more relevant as the news has gotten to be nothing more than a ratings-driven profit machine."

Or as Cher puts it in the AFI spoof: "It's a reflection of our time and that's what makes it great."

• Anchorman 2: The Legend Continues is released on 20 December.

• Ben & Jerry's to release Scotchy Scotch Scotch ice cream

• Ron Burgundy to publish tell all memoir