There could hardly be a more appropriate film to open the Venice Film Festival than Birdman, a jaw-dropping whirl of ideas about celebrity, art and ego starring Michael Keaton as an actor who achieved his now-faded fame as a rubber-suited super-hero called Birdman.

Venice is a festival both obsessed with its own tradition - we are reminded constantly that this is the world's oldest film festival - and permanently poised on the hinge between glamour Italian-style and a peculiarly rarefied European art cinema.

Models as well as actors pose on the red carpet, turning up the overall glitz level to 11. Meanwhile, the program includes a leavening of the kinds of films so obscure, so slow, so gloriously indifferent to anything resembling the marketplace that they make the festival seem almost contrarian.

Alejandro Gonzalez Inarritu's Birdman covers most of these bases in its first few minutes.

Keaton plays has-been star Riggan Thomson, who has sunk his savings, his energy and whatever talent he has into putting on his own adaptation of Raymond Carver's What We Talk about When We Talk About Love.

Desperate to prove himself as a serious artist, but almost as desperate to recover his old celebrity status, Thomson is likeable but pathetic; the same could be said of his cast of actors, including the absurdly self-important Shiner (Ed Norton), who has made his name on the stage and would never sully his talent by going to Hollywood.

In real life, of course, Keaton had his greatest success as Batman, way back in 1989 with director Tim Burton: this is only one of the cross-references between ideas of celebrity that, Inarritu told the press conference in Venice, constitute the "mirrors within mirrors within mirrors" in the film.

This year's Venice Festival includes several films about film culture, starting with Birdman and including documentaries about American directors Robert Altman and Arthur Penn, along with Abel Ferrara's biopic of Italian director Pier Paolo Pasolini, who directed the scandalous 120 Days of Sodom and was murdered, supposedly by a rent boy, in 1975.

Perhaps this is a year for reflection on what cinema - the seventh art, as Venice still calls it - is actually for.

The best answers to that question are usually to be found in the films about which the critics know nothing beforehand but which turn out to be revelatory. Venice has yielded up quite a few of these over the years, perhaps because the program has fewer well-thumbed names and expectations to fulfil than Cannes does.

That said, there are few names more guaranteed to build buzz than that of Al Pacino, who appears in Barry Levinson's The Humbling - another story of a washed-up actor, this time one embroiled in a May-to-September romance with a woman who defines herself as a lesbian (Greta Gerwig) - and David Gordon Green's Manglehorn.

Andrew Garfield, best known these days as Spiderman, appears in the recession drama 99 Homes, directed by Ramin Bahrani.

Also on the directorial side, there is the return of Peter Bogdanovich, the former Hollywood hell-raiser and director of long-ago '70s hits The Last Picture Show and Paper Moon, after 13 wilderness years. She's Funny That Way is a comedy starring Jennifer Aniston, Owen Wilson and Imogen Poots as a prostitute turned Broadway actress: its promised frothiness is very much at odds with the Bogdanovich legend.

And tucked away in a festival sidebar is a new film from Laurent Cantet, whose splendid film The Class won the Palme d'Or in Cannes a few years ago. His Return to Ithaca portrays five friends who meet up at an old haunt in Cuba and discuss past dreams and current lives.

One day in, there is plenty of critical love for Iranian director Mohsen Makhmalbaf's The President, a satirical drama about a deposed dictator who tries to flee his unnamed country by posing as a street musician.

Joshua Oppenheimer's The Look of Silence, a companion piece to last year's extraordinary The Act of Killing, gripped its first audience with the grim details of Indonesian genocide in 1965.

Birdman has also had rave reviews; there is a slight irony in this. It is "the old bat from The New York Times", gamely played by Lindsay Duncan, who tells the star that, sight unseen, she will review his play so badly it will close immediately. "I don't normally read critics," says Keaton, "but that's because I'm kind of lazy."

Do yourself a favour, Michael: read them tomorrow.