As a music fan or a moviegoer, you'd have every right to be skeptical about "Michael Jackson's This Is It" (two and a half stars out of four), the new collection of footage taken from rehearsals for the series of concerts the singer planned to give in London before his death. Those who treasure Jackson's music might have feared seeing their idol, at 50, as a diminished version of the man who changed the music world with his moonwalk more than 25 years ago; and anyone paying to see the film would have been justified in wondering if the whole project was just a way to cash in on Jackson one last time.

Turns out the cynicism in both cases is unwarranted. Jackson certainly wasn't the same performer he was at his , but "This Is It" proves that he desperately wanted to put on a great show is and all indications are that the London concerts would have been quite a spectacle. (The crew for the shows, we learn, included an "aerialist" and a "pole dancing expert.") The movie, meanwhile, has its problems, but at its best, it's a fascinating glimpse of a true genius at work and a bittersweet last look at one of the all-time great entertainers.

"This Is It," which was directed by the concert's director, Kenny Ortega, shows Jackson in control of himself and the show, a man who still cared deeply about his fans, despite the fact that many had turned on him a long time ago. The movie doesn't show much of the private Michael, and let's face it: Jackson's personal life had become more intriguing to many of us than his music. But whatever may have been going on behind the scenes, it wasn't affecting Jackson's work on stage.

The songs included in the movie are classics, from "Bad" to "The Way You Make Me Feel" to "Black or White" to "Billie Jean" to a medley of Jackson 5 tunes, and they were to have been performed to elaborate, and in many cases, inspired production numbers. Special effects wizards found a way to insert Jackson's image into a mashup of old film noirs like "Gilda" and "The Big Sleep" for his performance of "Smooth Criminal," and "Heal the World" included a rain-forest sequence that ended with a bulldozer plowing off a giant screen and onto the stage. In one of the film's highlights, we see the rehearsals for "Human Nature" dissolve into a more polished final number.

In between, Jackson collaborates with his fellow musicians and dancers (Michael still had amazing moves, it's clear from the start), never being the temperamental or highly medicated diva we might have expected. Jackson's instincts for the music were unerring. He uses an air guitar to instruct one musician on how a song should be played and teaches another to insert perfectly timed pauses into a piece of music to up the showmanship factor. It's not hard to see why those involved in the concert were awed by the chance to work with him.

But that's also part of the problem. Ortega was too awed by Jackson to include anything that would have even come close to portraying him in a negative light, and we feel as though we're only getting part of the story. "This Is It" offers a built-in excuse for this: It's a "gift" from Michael to his fans, and as such, should be expected to be the most positive spin on his final days. We'll never know if any more interesting storylines exist in the footage that was taken. I also wonder if Jackson, who's painted as a perfectionist in this film, would have wanted the public to see the unfinished product behind what was to be a very glossy show.

Again, we'll probably never know. Perhaps a better title for this movie might have been "This Is It: Take It or Leave It."

DOUBLE FEATURE

As farewell concert films go, the best by far is Martin Scorsese’s “The Last Waltz” (four stars), which documented the 1976 final concert of The Band. Scorsese weaves musician interviews with performances, which feature some of The Band’s greatest hits (“Up on Cripple Creek,” “The Night They Drove Old Dixie Down”) and collaborations with a number of guest stars, including Bob Dylan, Neil Young and Joni Mitchell. Muddy Waters’ searing performance of “Mannish Boy” is a personal highlight, but nearly every song is fantastic, and it all adds up to one of the greatest rock and roll movies ever made.