Grade: A-

Who could have predicted that the summer’s best comedy would be an updated version of “National Lampoon’s Vacation”? That John Hughes-Harold Ramis movie has been copied innumerable times, never happily, and most recently it was silently remade as “Johnson Family Vacation”–an atrocity of the first (or is it last?) order. But in “Little Miss Sunshine” it’s an obvious model–even the macabre Aunt Edna episode is present, albeit in cleverly altered form–and is refreshed rather than trashed. The new film puts a brilliantly fresh spin on the story of a dysfunctional family’s long road trip (here to a children’s beauty pageant rather than an amusement park), and ends up both wonderfully amusing and curiously moving. It’s this year’s “Sideways”–and you can’t get much better than that.

The centerpiece of the large ensemble cast inhabiting Michael Arndt’s funny and perceptive script is little Abigail Breslin, who plays Olive Hoover, a cute Albuquerque seven-year old with an obsession over beauty pageants keen to win the Little Miss Sunshine contest despite the fact that she’s slightly overweight and wears prominent glasses. That might make her a bit peculiar, but she’s still an oasis of stability within her highly fractured clan. Dad Richard (Greg Kinnear) is a failing motivational speaker desperate to land a publishing contract for his multi-step program, leaving mom Sheryl (Toni Collette) increasingly distraught over the family’s tight straits. Older brother Dwayne (Paul Dano), a surly teen who idolizes Nietzsche, despises his parents (and humanity in general, it appears) and is intent on becoming a fighter pilot, refusing to speak until he achieves his goal (he converses only rarely, and then via hastily scribbled notes). Then there are the relatives who live with them: Grandpa (Alan Arkin), an irascible, foul-mouthed codger who’s quietly training Olive in a routine for the contest, and gay Uncle Frank (Steve Carell), a world-famous Proust scholar who’s lost his professorship after attempting suicide because he was dumped by his grad student lover in favor of an academic rival and lost one of those MacArthur genius grants to the same competitor. One can imagine the scorpions-in-a-bottle circumstances that arise when they’re all forced to cram into a broken-down van to drive to California, where Olive has, by a curious chance, been invited to compete in the finals of the contest. The journey is filled with comic disasters and poignant interludes, and ends with a finale in which the family must come together to support the little girl in an environment that, in the wake of the whole Jon Benet Ramsey story, can’t help but be more than a little creepy.

One can imagine this tale being every bit as awful as the other “Vacation” imitators; but it’s not, thanks to Arndt’s witty and insightful script, deft direction from Jonathan Dayton and Valerie Faris (making their feature debut after a background in commercials and videos), and a cast without a weak link. Kinnear puts his smarmy, officious manner to good use as the uptight Richard, Collette combines reason and simmering anger as Sheryl, and Arkin has a field day as the deliberately outrageous grandpa. Best of all are Carell, whose deadpan amazement at everything is wonderfully wry, and Dano, who continues to impress as one of the more gifted young actors working today, bringing a mixture of low-key charm and touching vulnerability to Dwayne. And Breslin proves engaging without becoming annoying.

“Little Miss Sunshine” could be criticized on the one hand for following a familiar formula and on the other for its calculated quirkiness. But it freshens the formula and damps down the quirkiness to an acceptable degree. Technically it’s little more than competent. But its lack of flash keeps the emphasis on the characters, which is precisely where it belongs. By the time it’s over you’ll be pleased to have spent a couple of hours with the Hoovers, and probably will have glimpsed a bit of your own family in them, even if (one hopes) in exaggerated form.

The picture, it should be noted, is distinctive in another way: it was a favorite at this year’s Sundance Festival, which is usually the kiss of death. (Remember “Happy Texas”?) This time, though, the Sundance curse has not struck. This bittersweet comedy-drama is a genuine jewel.