SOMEDAY, SOMEONE is going to make a hell of a movie about Michael Jackson. Jackson's life was fascinating enough—and fucking weird enough—to spawn at least one cinematic retelling, but really, there could be one in every genre: an Astaire-style musical, a Ken Burns documentary, a Cronenbergian body horror flick. If that ever happens, at least one of 'em will be great.

Michael Jackson's This Is It isn't great, but then, it never claimed to be—it's an obvious, shameless, and rushed cash-in. (For those keeping track, Jackson's been dead for all of four months.) The film's directed by Kenny Ortega, whose achievements include High School Musical and Hannah Montana's concert movie; he was also a "creative partner" for Jackson's ill-fated comeback concerts.

The footage from This Is It is culled from rehearsals for those concerts, and the product is less a concert film and more a rehearsal film: After running through performances, Jackson looks like a brittle skeleton as he gives bewildering instructions to various yes men. ("Just bathe it in moonlight—you have to let it simmer," he tells the show's musical director about "The Way You Make Me Feel.")

Despite Jackson's frailty—the cameras keep their distance, rarely giving us a good look at his papery, gaunt face—he could still move, and here he does so with a vigor and grace that, even now, astonishes. Skittering and gliding across a massive stage, Jackson leads a squadron of dancers who are a third his age.

Those dancers, along with members of the band, contribute a few mewling sound bites, but This Is It is mostly hastily edited rehearsal footage combined with reimagined versions of Jackson's groundbreaking music videos. (These things, also directed by Ortega, are miserable little abominations—particularly the neutered "Thriller" redux, in which John Landis' landmark video is remade into something resembling Disneyland's Haunted Mansion.)

There are other weird moments, too, from a performance of the Jackson 5's "I'll Be There" in which Jackson is accompanied not by any of his brothers but by four generic background singers, to a depressing moment when Jackson explains his vocals are lackluster because he's saving his voice for the concerts. Most awkwardly, Ortega structures This Is It not as a documentary but as a tribute, and all the preaching starts to drag.

More effective are the film's too-rare flashes of accidental insight: Sometimes Jackson gets embarrassed, or jokes, or cracks a small smile, and when that happens, he briefly seems human and vibrant—one sees him not as the ensconced, eerie freak he became in the '90s, but as the exhilarating, charismatic showman of the '80s. Not even the greedy, glossy idolization of This Is It can diminish the power of those moments—nor the ones when the drums and the bass of “Billie Jean” and “Smooth Criminal” and “Beat It” thump out, clear and loud, from a movie theater’s powerful speakers.