When your film languishes for more than a decade in development hell before eventually getting an OK from the suits, the result is usually a case of what might have been. But Kevin Lima's fantasy romance, which begins with 10 minutes or so of hand-drawn animation and then sends its leading character into the streets of contemporary New York, manages to buck the trend.

It looks fresh and original, as if it were made in a flash of inspiration rather than over years of painstaking labour. Its triumph is as much due to its star, Amy Adams, as anyone else. Her seemingly guileless but utterly artful and convincing performance as the cartoon princess who lands up in a real-life romantic fix is what gives Enchanted its edge.

Adams, who was nominated for an Oscar and might have got one in another year for her totally different kind of performance in Junebug, is Giselle, a princess in the animated kingdom of Andalasia, who falls in love with a handsome prince (James Marsden) but is thwarted by Susan Sarandon's evil Queen Narissa and her portly henchman (Timothy Spall).

They contrive to throw first her and then the prince out of the enchanted kingdom that Narissa rules and down to earth through a manhole in New York's Times Square. That's the place, says the Queen, where nobody is happily married, however much they thought they were in love at first. Poor Giselle is in a lavish ballgown at the time, which makes getting through the manhole difficult and through the doors of Patrick Dempsey's divorce lawyer's flat almost impossible. He has picked her up in the street after a tramp has stolen her tiara.

The girl, who has never heard of such things as stealing or even anger, is now in a rough, tough world where very few have ever heard of generosity and kindness. But she soldiers on, like a modern Snow White or Cinderella, perkily hoping for the best and even calling on the animal kingdom she has known from the animated world of Andalasia to clean out the nice lawyer's flat.

These include rats and roaches who like her innocence as much as Manhattanites hate them. And now the question is whether the lawyer, whose daughter tries to get her into contemporary clothes and regards her as a potential step-mother, will begin to like her too.

Of course he does. Which means, when the prince emerges from the manhole looking like a refugee from an oldstyle pirate film, there is certain to be trouble ahead. We know, however, that nothing untoward will ever happen since this is still essentially a fairy tale, even in a different mode from its beginning.

Enchanted progresses in much the same style when in real-life form as it does in its animated prologue. It is sentimental, quite silly and determinedly old-style Disney throughout, while maintaining a very slightly knowing and ironic touch too.

It uses computer-generated effects at the end and in the middle as well - but the opening hand-crafted animation beats it to a frazzle. How good to see it again these days, even if it tends to parody the Disney style with its sweetly chirping birds, anthropomorphical chipmunks and other denizens of the forest.

If Enchanted is no great shakes in total, and the music and songs from Alan Menken are not exactly memorable, its conception is unusual enough, and spirited enough in its execution to entertain more than the children, even if it is still aimed shrewdly at younger audiences.

And no one could possibly complain about the sustained perkiness of Adams's performance, which refuses parody but has a twinkly-eyed innocence likely to charm even Manhattan, let alone us.