Right now, the Buffy creator is the hottest property in cinema with the acclaimed The Cabin in the Woods and soon-to-open superhero movie Avengers Assemble. And then it's on to Shakespeare

Just one top-five, praised-to-the-rafters movie in the space of a year would be the pinnacle of most film-makers' careers. Two in a fortnight is surely beyond the fantasies of anyone whose name does not include the words "Steven" and "Spielberg". And yet it is precisely this exalted position in which the jolly, unassuming 47-year-old Joss Whedon now finds himself.

Earlier this month, the man best known as the creator of the beloved cult TV series Buffy the Vampire Slayer dazzled critics and audiences with The Cabin in the Woods (which he co-wrote with the movie's director, Drew Goddard). Putting a subversive spin on multiple manifestations of the horror genre, from slasher to zombie to monster movie, it has been widely celebrated for a witty postmodernism not seen since Scream.

Admirers of Whedon will know that playfulness is the lifeblood of his work: Welcome to the Hellmouth, the 1997 debut episode of Buffy, featured a memorable scene in which an apparently vulnerable high-school girl, who seems about to be ravished by her date, sprouts a pair of fangs and leaves him somewhat the worse for wear.

As well as indulging this taste for upending our expectations, The Cabin in the Woods also represents a chance for Whedon to rescue the horror genre from the clutches of torture-porn such as Saw and Hostel. "A really, really well-crafted horror movie can be an end in itself," he says. "It's just that my feeling has been lately that a lot of horror movies have made a horrible death an end in itself, instead of the actual film, the horror experience." That's Whedon all over. He doesn't just scare: he cares.

The Cabin in the Woods, shot in 2009 but shelved when its studio, MGM, went bankrupt, is still playing to sell-out audiences here and in the US, even as Avengers Assemble is poised to join it at the multiplexes. If Cabin has given Whedon a taste of the attention he enjoyed at the height of Buffy's success, it is about to be eclipsed by this superhero extravaganza that brings together Iron Man, Thor, the Hulk and Captain America, like a school reunion with added Spandex.

Individual films featuring those heroes have grossed more than $2bn worldwide, so it would not be unrealistic to predict that the combination of a multi-hero blockbuster and Whedon's golden touch could make it the most successful superhero movie in cinema history. Early reviews have been passionate: Variety magazine called it "buoyant, witty and robustly entertaining", while the verdict of film site CinemaBlend ("One of the most entertaining and satisfying comic-book movies yet") is typical of the level of online fervour.

Whedon, who lives in Los Angeles with his architect wife and their two children, has shown an enviable knack throughout his career of being able to satisfy the fanboys and girls who make up Hollywood's coveted 15-25 target audience, all without ever patronising them. If anyone can make a movie that articulates and embodies the appeal of superheroes, while also taking the material to a new level, it is likely to be Whedon. Fantasy has never been frivolous for him; he takes entertainment and escapism seriously. For all that Buffy the Vampire Slayer was brimming with horror folklore and girl-on-vampire martial arts action, it was essentially a programme about growing up. No wonder its adolescent audience responded so emphatically.

Whedon didn't talk down to his young fans, nor did he regard television as an inferior medium to film, even back in those days before prestigious US hits such as The Sopranos, The Wire or Sex and the City began to render cinema's supremacy moot. Coming from two generations of television sitcom writers may have played some part in that – his father, Tom, was a writer-producer on The Golden Girls and Benson, while his grandfather, John, had worked on 1950s US sitcoms including Leave It to Beaver and The Andy Griffith Show.

"At first, I was like, 'I shall never write for television'," says Whedon. "I was a total snob. I never watched American TV, I only watched, like, Masterpiece Theatre. And I was like, 'Television is lame-o, I am a film student, I shall never write for... they pay how much?' I'm still a complete snob, but it's reversed. I feel like film is a ridiculous hell and TV is the greatest place in the world."

After graduating with a film studies degree and dispatching a few spec scripts, Whedon was hired as a staff writer on the late-1980s sitcom phenomenon Roseanne, where his ability to capture the female voice impressed the show's star, Roseanne Barr. It's no small part of Whedon's latterday appeal that he has introduced strong female characters into genres too often monopolised by men; several years ago, he was even instrumental in trying to get a Wonder Woman film off the ground.

This fascination with powerful women comes, he has explained, from his mother. "She was an extraordinary inspiration – a radical feminist, a history teacher and just one hell of a woman. What she did was provide a role model of someone who is completely in control of her life. It was only when I got to college that I realised that the rest of the world didn't run the way my world was run and that there was a need for feminism. I'd thought it was all solved."

Even if Avengers Assemble is regrettably low on female superheroism, save for Scarlett Johansson as Black Widow, Whedon's efforts to counter what he calls Hollywood's "very casual, almost insidious" misogyny go back a long way. Buffy made her first appearance in a poorly received and rather scrappy 1992 movie, Buffy the Vampire Slayer. "The first thing I thought of when I thought of Buffy – the movie – was the little blonde girl who goes into a dark alley and gets killed in every horror movie. The idea of Buffy was to subvert that idea and create someone who was a hero where she had always been a victim."

Despite that film failing to find favour either with audiences or its own creator, Whedon landed a series of writing gigs, both credited (Toy Story, Alien Resurrection) and uncredited (Speed, Waterworld, Twister), which paid handsomely and demonstrated his wit and skill. In 1997, he resurrected Buffy on television; over the course of seven seasons, the show attracted a fanbase to rival Star Trek's Trekkies, the previous high-watermark for televisual fan hysteria.

"I designed Buffy to be an icon, to be an emotional experience, to be loved in a way that other shows can't be loved," Whedon said. "Because it's about adolescence, which is the most important thing people go through in their development, becoming an adult. And it mythologises it in such a way, such a romantic way – it basically says, 'Everyone who made it through adolescence is a hero.'"

In this way, Whedon also predicted and catered for the incipient obsessive sensibility that would be nurtured by the internet. Although chatrooms and message boards were in their infancy when Buffy began, the show went on to develop an online presence that persists today.

In her BFI study of Buffy the Vampire Slayer, the critic Anne Billson argues that the internet is where Buffy found its feet, bridging "genders, geographical distances and generation gaps in a way no television show has done before". Online word of mouth was instrumental in the enthusiasm for Whedon's subsequent shows – the Buffy spin-off Angel, the science-fiction western Firefly and the bizarre Dollhouse – but in some cases there was a disparity between the fans and the commissioning channels. Firefly was cancelled abruptly after only 11 episodes had been broadcast, leaving a dejected Whedon to continue the show's story in his first film, Serenity. Dollhouse was dropped after two seasons and even Buffy jumped ship from Warner Bros after its fifth season when a Warner executive dismissed it as "not a show… that stands above the pack".

Regardless of the vagaries of the television networks, Whedon has amassed a dedicated following that guarantees interest in his dizzying range of projects, from graphic novels and comic books to instalments of his internet musical Dr Horrible's Sing-Along Blog to directing episodes of the US version of The Office. There's even a micro-budget, monochrome version of Much Ado About Nothing, which he recently finished shooting, on its way to cinemas.

That's a lot of fingers in a lot of pies, all with wildly contrasting flavours. Those of us drawn to movie websites or science-fiction conventions, into comic-book stores or cinemas, could be forgiven for thinking that it's Joss Whedon's world and we just live in it.