Senna, Asif Kapadia, 105 mins (12A)<br/>Donor Unknown, Jerry Rothwell, 78 mins (12A)<br/>X-Men: First Class, Matthew Vaughn, 110 mins (12A)

Two of this week's documentaries could have been concocted by a Hollywood screenwriter – although if you saw their plots in a fictional film, you'd probably scorn them for being too far-fetched.

Take Senna, for starters. Its hero is a good-looking Formula One driver who becomes a national hero in a country that's starved of inspiration. He's ferociously competitive and apparently fearless on the race track. Off it, he's soft-spoken and religious, and he has no patience with the politics that pollute the sport. When he wins a Grand Prix on his home turf he completes the last few laps with a broken gearbox, and he's in such agony afterwards that he can barely lift the trophy above his head.

Beat that, Rocky.

The cinematic qualities of the late Ayrton Senna won't come as a surprise to F1 fans, but for the rest of us this extraordinary documentary is a revelation. Asif Kapadia, the director, has sifted thousands of hours of television and home movie archive, and the footage he's unearthed is almost too good to be true. In-car cameras give a stomach-tightening sense of what it's like to hurtle around Monaco's roads at insane speeds, while the scenes of Senna and arch-rival Alain Prost sniping at each other are, again, the stuff of Hollywood.

Kapadia has shaped this astonishing source material into a riveting, intensely moving tragedy, all without using a narrator. Some context is provided by snippets of voice-over from the driver's associates, but when you've got a personality as large as Senna's on film, you don't need much else.

If Senna may come to be regarded as a classic sports movie, Donor Unknown could be seen as a classic indie comedy – even if it, too, is a documentary. It's the mind-blowing tale of a young woman who was conceived via an anonymous sperm donor. With the aid of the internet, she locates not just her biological father, Jeffrey, but the many half-siblings who are also the fruit of Jeffrey's loins. There are some spooky similarities to The Kids Are All Right – one lesbian mother even looks like Annette Bening – but the writers of that film would have never dared make the Mark Ruffalo character as extreme as Jeffrey. Unbelievably, he's a spaced-out Iggy Pop clone who lives in a junk-cluttered van in a Venice Beach car park, where his best friends are dogs and pigeons.

Ultimately, the documentary raises more issues than it explores – there are some tough ethical questions that a certain Californian sperm bank needs to answer – but the human-interest story it tells is a joy. It's worth noting, too, that both Donor Unknown and Senna, despite their international subject matter, were made by Brits. Factor in TT3D: Closer to the Edge and the forthcoming Life in a Day, and 2011 could be the year of the British documentary.

X-Men: First Class is one of the many Batman Begins/Casino Royale-type prequels, which go into unnecessary detail about their heroes' formative years – as if anyone needed to know how Professor X got his team of mutant superheroes together. But, as redundant as it may be, the film stands out from the prequel crowd by being set in the early 1960s and having so much fun with its period setting. Professor X (Patrick Stewart in the original trilogy) is a silver-tongued Oxford post-grad played by James McAvoy. Meanwhile, the young Magneto (Ian McKellen in the first films) is a dashing Nazi-hunter played by Michael Fassbender with more than a dash of James Bond and Harry Palmer. When Magneto and the Prof team up against Kevin Bacon and January Jones's Austin Powers-ian villains, the film becomes a swinging spy caper, complete with mini-skirted CIA agents, Booker T songs on the soundtrack, and a brush with the Cuban missile crisis.

Eventually, X-Men: First Class goes the way of all superhero films, and the groovy espionage is buried under an avalanche of unconvincing computer-generated action. But before that it marries a shrewd sense of humour with sharper-than-usual handling of the mutants-as-persecuted-minority theme. In the saga's next outing, I'll be disappointed if Professor X doesn't meet Malcolm X.

Next Week:

Nicholas Barber gets Point Blank in his sights, another French crime thriller from the writer-director of Pour Elle

Also Showing: 05/06/2011

Last Night (92 mins, 12A)

When Keira Knightley's husband, Sam Worthington, goes away on business, he's tempted by a colleague, Eva Mendes, while Knightley is tempted by an old flame, Guillaume Canet. It sounds promising, but this bloodless bunch of Manhattan socialites would rather lounge around their hotel suites discussing the concept of adultery ("It's natural to crave a newness," muses La Knightley) than indulge in it. Besides, Knightley and Worthington are never seen together except when they're having a row, so it would hardly matter to us if they switched to the prospective partners who are conveniently available to them both.

Screwed (110 mins, 18)

A retired soldier (James D'Arcy) finds working as a prison warden a hell of a lot more stressful than it looked on Porridge, thanks to the threats from the inmates (including Noel Clarke) and the corruption of his colleagues (including Frank Harper). It would make a decent TV series.

Rio Breaks (82 mins, 12A)

A profile of the Favela Surf Club, which provides free surfing lessons – and, potentially, a whole new life – to children from the slums of Rio de Janeiro. If only the director had chosen to point his cameras at two boys who actually did some surfing, instead of two who spend most of the film chatting and mucking about on the beach.

The Flaw (82 mins)

This upbeat analysis of the financial crisis made matters slightly clearer to me – but only slightly. After a while, the graphs and statistics and triple-A mortgage-backed securities begin to blur, and the ironic, Michael Moore-ish appropriation of 1950s public information films doesn't help.

Prom (104 mins, U)

In movies, high-school proms are usually the settings for grisly murder sprees or hormone-crazed sexual blunderings. Tragically, neither is in evidence in this blander-than-bland Disney comedy-drama.