For Joss Whedon fans, part of the fun has always been banging on about how underrated he is and how his screenplays and teleplays are never given the kudos they deserve. So now we have an interesting development. The Cabin In The Woods is being touted and trumpeted as one of the greatest horror movies of modern times. Hyped to the max as "a game-changer", the first UK preview screening early this year had those of us present signing our first-born away in the name of secrecy. This we submissively did, as Whedon graced us with a brief personal intro. "I hope you love it," he said. "If you don't, you're wrong."

More than any film's press campaign I've known this century, this movie's minders have begged, pleaded and scolded to ensure we don't reveal any twists or spoilers. Which makes reviewing it very difficult, nigh on impossible. We can give the stock scenario: a standard youths-in-peril set-up, after which all hell breaks loose. Five friends meet cute and leave campus in their camper van for a getaway in a cabin. In the woods. (Yes, The Evil Dead is referenced, as are countless other genre giants, even H.P. Lovecraft). There's the jock (Chris Hemsworth, aka Thor from the Marvel superhero adaptation), the blonde (Anna Hutchison), the bookworm (Jesse Williams), the sort of virgin (Kristen Connolly) and the stoner (Fran Kranz, who Whedon obsessives will know as the irritating Topher Brink from Dollhouse). On the road they encounter a creepy redneck 'harbinger', who sagely mutters, "I've seen plenty come and go." But already things are weird, a little off: the whole show so far is being observed by a deliberately mundane yet mysterious office-laboratory, bossed (we think) by Bradley Whitford (The West Wing) and Richard Jenkins (Six Feet Under). This film, we're thus told, is going to be very, very meta.

Of course - of course - the gang run into scary goings-on. And with dialogue from Whedon and director Drew Goddard (the latter was a frequent Buffy squad-writer with further script credits on Lost and the 2008 feature Cloverfield), it's all highly knowing and tartly smart-ass. As the crew move stuff around in the dusty basement, Kranz' Marty sighs, "I'm drawing a line in the fucking sand here. Do NOT read aloud the Latin..." But there are layers and levels and double bluffs and magician's reveals which suggest Whedon and Goddard wanted to see how crazed they could possibly get with stretching and subverting the conventions. Often, what they do here is brilliant. And, once or twice, this viewer found it all a little silly, a bit turn-it-up-to-11-just-because-we-can. Infuriatingly, my hands are tied and I can't elaborate. If you're a Whedon fan, you simply have to see it. If you're not, you probably will anyway, as the film's being pushed to opening night moviegoers who'd zombie-walk along to the weekend's big Friday 13th release if its tagline was 'Ooh! Scary! Possibly with chicks in tight tops! And some blood.'

What with the presumably even bigger Avengers Assemble also imminent, Whedon is about to hog the mainstream. At last. Which is fine. But for those of us who've championed for years his groundbreaking, era-defining scripts and productions with Buffy The Vampire Slayer, Angel, Firefly, Serenity and Dollhouse - each of which was treated less kindly by schedulers and publicists than merited - spring 2012 is a watershed. It's a bit like – well, it's exactly like – when that cool, semi-obscure band you've clasped to your bosom and bonded over with tuned-in friends through four or five cult albums suddenly goes supernova and starts filling stadiums with work that's... good, but not quite as good as what made them special. It's the moment some of us start snottily saying that we preferred his formative, less celebrated efforts.

Not that Buffy was unknown, for sure. It was a slow-burning, sleeper phenomenon, which overcame a false start (the flat 1992 movie) to become the smartest, sassiest show on air. Its middle name was post-modernism. Characters critiqued their own switchbacks. Buffy, Spike, Giles and Anya were as conflicted, multivalent, sexy, funny and intriguing as any, ostensibly more grown-up, HBO lead. The narrative threads got darker and darker (their notion of 'hell' as bleak as that of any existentialist) while stand-alone episodes such as 'Once More, With Feeling' (a musical) or 'Hush' (two-thirds of which was silent) can even now take your breath away with their depth, wit and verve.

Angel, the spin-off, never won equal recognition, but as good-vampire private-detective concepts go it's never been matched. It too was savvy enough to learn from early season errors – dumping lame characters, bringing in better ones, grasping the fact that we wanted it to go more adult, more focused on sex and death – and bowed out gloriously. Space western Firefly and big screen sci-fi sister Serenity (2005) stuttered, but Dollhouse recovered from hiccups (fine-tuning in situ is a Whedon trait that pays dividends but which helps us understand why commissioners have been so cautious with him) to reach compelling levels of high drama and low eroticism that wed Belle De Jour to Blade Runner. Always, there were the one-liners, as zingy as a Generation Y Groucho Marx. I could lazily paste a few here, but if you're a convert you'll already have them tattooed on your flesh, and if you're not I'll give you the chance to discover there were great things on TV before The Guardian told you you're only allowed to like The Wire and The Killing. (Or Mad Men, if you're one of the five people who has the necessary Murdoch channel.)

The Cabin In The Woods, then, both amps up and deconstructs the fright genre, with a dash of reality TV parody and lines like, "Oh yeah, I had to kinda dismember that guy with a trowel. What've you been up to?" A "game-changer"? That was said about Kevin Williamson's Scream (1996), which similarly put the words of stand-up comics and philosophers into the mouths of wise-ass babes. Will it pull focus away from torture porn (the Saw franchise, Hostel, etc) and mark a revival of some, as opposed to no, brain? We can hope. Is it as good as it's cracked up to be? I'm not sure that, for example, commenting 'wryly' on the predictability of the hottie taking her top off then having her take her top off is all that iconoclastic, but the visual effects blow-out of the final half-hour (I think I'm allowed to say that much without a press office sniper taking me out) is certainly a wild, memorable crescendo. Does that noisy firework display in itself - and the arrival of a big star cameo - defeat the object of all the knowingness?  No, because it's all explained. Sort of. It's just that - by law - I can't explain it. This film is worth seeing. Me, to paraphrase Woody Allen's Stardust Memories, I preferred Whedon's earlier, funnier work.