One of the less enjoyable aspects of reviewing films is having to watch the movies that are made for children today. For the most part they feel like mere products. Even when they are drenched in treacly sentimentality they reek of commercial calculation and cynicism. Sometimes they are made insufferable by condescending efforts of the filmmakers to seem “cool”. Even more irritating is their tendency to follow the tiresome Hollywood convention according to which kids have to be shown as smarter than their parents.

Up is something completely different. It is a film made for children that is truly satisfying for adults. Moreover it is brilliant: genuinely moving, intelligent, exciting and funny.

The first animated film ever to open the Cannes Film Festival, Up is up there with the works of the great Japanese animator Miyazaki and the best of the original Disney films of the mid-20th century. I would argue that it is not just the best animated film to come out in some years, but probably the best film of 2009.

Put baldly, it is a story about a grumpy old man who floats his house up into the sky using balloons and takes it to a remote South American valley, in the company of a rather hopeless eight-year-old boy. There, the old man embarks on the high adventure that he himself had dreamed of as a film-struck child in the 1930s. But no such simple description does Up justice.

The first third of the film is about the early life of Carl Fredricksen (voiced by Ed Asner), his childhood adoration of leather-helmeted explorer Charles Muntz (Christopher Plummer), and his meeting a like-minded little tomboy called Ellie who eventually becomes his wife.

A long montage evoking their lives together may be one of the most poignant animated sequences ever made. (The film’s treatment of issues of love, age and regret is so heartfelt and honest that it would be a surprise to encounter it even in an adult live-action work).

Carl is a sad and crusty widower when he encounters Russell, a roly-poly little boy involved in a present-day cub scout organisation called Wilderness Explorers. (Interestingly, Russell is not nearly as knowledgeable or well-educated as Carl and Ellie were at the same age.) But it is not Russell’s influence that prompts Carl to blow up thousands of helium balloons and launch his little wooden house into the sky — it is the threat of eviction and resettlement in an old people’s home.

Carl and Ellie had always dreamed of going to Paradise Falls, the “lost world” first explored by Charles Muntz back in the ’30s. And when Carl and the boy Russell finally land on a mesa, a flat-topped hill near Paradise Falls, they come across some extraordinary things. These begin with a giant exotic bird, and a dog that someone has fastened with a high- tech collar that gives it the ability to speak its easily distracted mind, but they culminate in a rather darker discovery inside the huge (spectacularly envisioned) zeppelin built decades before by Charles Muntz.

One of the many pleasures of Up is the way it cleverly weaves some delightful jokes (often involving Dug, the speaking dog) with scenes of pathos and thrilling action. Another is its visual beauty. The Pixar animation studios changed the cartoon world with Toy Story in 1990. Up is their 10th film and it makes gorgeous use of even more advanced technology to make wonderfully detailed and deftly lit images, and if you see the 3D version you will be amazed at how “real” they look.

Yet all this breathtaking technical virtuosity is not allowed to overwhelm the story, the roundedness of the characters, or the sincerity of the film’s message which is that life’s greatest adventures are not necessarily to be found “out there”. The music is lovely too. Never intrusive, it enriches what you see on the screen.

In America Up had a PG rating and I would not recommend it for very small children: the mean dogs in it are much more frightening than most cartoon villains. Indeed, there were many times when I wondered if Up is not really an animated film for grown-ups with some goofs for children thrown in.

The film is directed by Pete Docter (who also directed Monsters Inc and wrote Toy Story) and Bob Peterson from a screenplay that they wrote with Tom McCarthy. And there is a remarkable coherence to the finely textured vision that found its way onto the screen. It is a work that wears everything lightly, from the subtle homages to other films, including classic silent movies, to the dramatic punch of 3D imagery.

There are few recent films that I would happily see twice; I look forward to taking any number of cousins, nieces and nephews to Up again and again.