`Wilde', released today, shows Stephen Fry perfectly cast to bring out the ambivalence in Oscar's sex lives. Julian Mitchell has had the immense advantage of being able to base his screenplay for Wilde on Richard Ellmann's biography, and the result shows more of the man's facets than could be presented before. There is a greater sexual explicitness, unsurprisingly - enough to show that Oscar Wilde's adventures with his own sex could be sordid as well as romantic. But his marriage is shown to be much more than a convenience, even if Oscar's first reaction to Constance's pregnancy was pleasure at the prospect of picking out a whole new wardrobe for her.

This Oscar Wilde is neither angel nor devil. It's true that there are hints of Christliness, but they are lightly sketched in: we first see him on an ass, riding into a Colorado mining town in 1882. When he is being taken away to Reading Gaol, he is reviled and spat on, and there is an explicit reference to the Crucifixion near the end of the film.

More in the foreground as an image of Wilde is his own character, the Selfish Giant. This was a charming parable unselfconsciously improvised for his sons, and consequently intended for publication. Mitchell sees the irony of a father's love-gift having to stand in for the man himself, when Constance, unable to supply Daddy in person, can at least take Daddy down from the shelf and read her children to sleep with his words.

The Giant in Wilde's story comes to understand and atone for his selfishness: in Mitchell's screenplay, there is a sort of provisional resolution to the Selfish Giant strand - an Act 1 curtain, as it were - with Oscar returning to his wife and sons, even after his first intimacies with Lord Alfred Douglas, and resolving not to neglect them again. This moment allows an audience to contemplate a 19th century in a parallel universe in which Wilde manages to balance his impulses and avoid catastrophe.

When he pursues his passion for Bosie, though, he is not more cautious but less. Wilde's mind had a taste for reversals of role and power, as several lines in the film demonstrate. He asks Bosie, on first meeting him, "At which college do you educate the fellows?" He asserts that only the young have the experience to judge his work. Even when he's telling his boys not to accompany him to get ice-creams, he says: "Stay and look after Nanny." So there was a sort of logical perversity to his putting himself in the power of the dreadful Bosie (played here by Jude Law), who did at least have experience of an underworld that Oscar hadn't previously visited.

It is no more than the truth to say that Wilde would be nothing without Stephen Fry, since the casting of the lead preceded the selection of a scriptwriter. Fry has a lot of advantages in interpreting the role, from rough physical similarity to a reputation for wit. Even his disadvantages don't hold him back: the asymmetry of his face - nose, mouth and chin unconventionally aligned - means that the difference between a smile and a smirk is often hard to detect.

It was to be expected that Fry would be expert at those parts of Wilde's persona that are approximate to his own - irony, suave subversiveness - but he handles remarkably well the moments when Wilde's own experiences take him beyond the protection of his polished reflexes. When he is initiated into homosexuality by Robbie Ross (Michael Sheen), his first reaction is not pleasure or even excitement. There is pure pain in his eyes as Robbie's trews descend.

When Bosie takes him to a brothel, Oscar seems to be at ease in character, indulging in an elaborate comparison of the boys to exotic blooms, but Fry lets us see that, for once, Wilde is out of his depth. His verbal flamboyance seems to be no more than self-deceiving, and everyone in the room knows why he is there.

Wilde is handsomely mounted but timidly filmed by director Brian Gilbert. His use of film language is unadventurous - only once does framing or camera work add anything to the performances, and that is when Wilde accepts his ovation for The Importance of Being Ernest. He walks forward tentatively, almost in fear, and Gilbert cuts to an angle from which the audience isn't visible, Oscar alone on stage. A man who stands centre stage has nowhere to hide.

Debbie Wiseman's music is at its best when it finds a sort of Satie mood of skewed elegance, but towards the end of the film her musical gestures become full of hectoring pathos. It can only be a mistake to pull out all the stops in this way, while telling the story of a man who found the death of Dickens's Little Nell so reliably amusing.

`Wilde' (15) goes on general release today