Tetro, Francis Ford Coppola, 120 mins (15)Whatever Works, Woody Allen, 92 mins (12A)

Two cinema giants do their best to trash their reputations with a story of unrecognised genius – and old guy gets girl

A few years ago, Woody Allen made an appalling film called Hollywood Ending.

It was a painfully flat comedy about an inept director who went blind, then made the worst movie ever – only to find it hailed as a masterpiece in France.

This is not such a surreal conceit. The French do have a habit of taking the strangest films to their hearts – including Hollywood Ending itself, which was given the prestigious opening-night slot in Cannes. Or take Francis Ford Coppola's new film Tetro – a pompous, shallow, callow, over-blown piece of phoney romanticism, which ended up on the front cover of Cahiers du cinéma, hailed as a magnificent return to form. All I can think is, whatever would Jerry Lewis say?

A swift follow-up to Coppola's equally dire Youth Without Youth, Tetro is Phase Two of the old master's late-period comeback. A while ago, he announced that he was embracing digital video as a way of making the sort of films he dreamt of as a young man – his idea of "student movies". Tetro is certainly a film that a student could have made – a student with too much money and a lot of grandiose notions yet to be knocked out of him.

Set in Argentina and shot mainly in black and white, Tetro is about an American teenager, Bennie – relaxed newcomer Alden Ehrenreich, a real find – who stops off in Buenos Aires to visit his estranged older brother, who now goes by the name of Tetro. Supposedly a creature of phenomenal brilliance, Tetro never produced the world-shaking literary oeuvre that he was destined for. Played as a one-note scowling neurotic by Vincent Gallo, Tetro is described by his long-suffering girlfriend (a sympathetic and stylish Maribel Verdu) as "like a genius ... without enough accomplishments". That's one way to sum up the self-aggrandising Gallo, whose legendarily inept The Brown Bunny hangs in a special place on American indie cinema's wall of shame (although it was lauded to the skies by Jean-Luc Godard, no less. QED.)

Tetro's talent, it seems, stalled because of an unresolved conflict with his brilliant conductor father – played in colour flashbacks by Klaus Maria Brandauer. Fortunately, Bennie vindicates Tetro's greatness by transcribing his scrawled memos into a play that gets its big chance at the Patagonia Festival. This swanky event, overflowing with champagne and Swarovski bling, is presided over by the mysterious "Alone" (Carmen Maura), "the most important literary critic in South America", who edits a magazine "with millions of readers".

You might wonder what world Coppola is living in. The world of a successful Californian vintner indulging his art-cinema fantasies. Tetro is utter tosh – a posh-pulp farrago of sex, travel and tormented genius, full of hot-blooded Latins and zany thespians being spontaneously creative (as in a godawful avant-garde striptease version of Faust, which Tetro the man mercifully heckles to a standstill).

What makes it all worse is that Tetro the film is undeniably carried off with the panache of a once-great director. Shot for shot, it looks fabulous. Cameraman Mihai Malaimare Jr gives the images an imposing lustre, especially in the nocturnal chiaroscuro: Buenos Aires has rarely looked so magnificent on screen. There are some insanely opulent fantasy sequences in colour, in tribute to Powell and Pressburger, and a sumptuously moody score by Osvaldo Golijov. But the sheen is wasted on a self-important bagatelle, putting you in mind of the Elvis Costello song, "All This Useless Beauty". Tetro is a rich man's folly, and from the maker of The Godfather and the superbly controlled, economical The Conversation, that's painful.

But at least Coppola is still pursuing his idea of cinema as cinema. There's very little cinema – and as little in the way of ideas – in Woody Allen's Whatever Works. This may not be Allen's worst ever – it's not quite Hollywood Ending or Cassandra's Dream – but it still has next to nothing going for it. Larry David plays Boris, an embittered ex-physicist now given to venting his spleen. One day, he reluctantly offers shelter to a gauche Southern waif (Evan Rachel Wood) and, as happens between young girls and cranky old men – at least in Allen's world – she falls for him. They marry, although their relationship seems somewhat chaste, as Boris is more interested in kvetching than leching. Then her old-school bigot parents turn up, and before long, they too are also transformed by Manhattan's bohemian delights.

Whatever Works is, by all accounts, a reworked version of a 1970s script that Allen took out of mothballs, though its story of Southern squares turned on by hipster city life feels more like stale '67 vintage. Boris's habit of making sour wisecracks to camera makes the film feel like a stilted stage farce, and Larry David's performance follows suit. Fans of Curb Your Enthusiasm should curb theirs fast: David's distinctive anti-charm here becomes horribly grating. Although the misanthropy is played for ironic laughs, Boris's prolix sourness too obviously voices Allen's well-known impatience with the modern world. Whatever works, it ain't this.

Next Week:

Jonathan Romney watches Isabelle Huppert in White Material, the latest from French filmmaker Claire Denis.