Jackson is the first artist to top The Billboard 200 posthumously since The Notorious B.I.G., who scored in March 2007 with Greatest Hits. This Is It posted the biggest posthumous weekly sales tally since an earlier Biggie album, Duets: The Final Chapter, which sold 438,000 copies in one week in December 2005.
This Is It reaches #1 by displacing another theatrical movie soundtrack, The Twilight Saga: New Moon. This marks the first time that theatrical movie soundtracks have topped the chart in back-to-back weeks since July 1998, when Armageddon replaced City Of Angels in the top slot.
This Is It is the first soundtrack to a concert movie to reach #1 since U2's Rattle And Hum logged six weeks on top in 1988. Two recent soundtracks from concert movies reached #3: Miley Cyrus' Best Of Both Worlds Concert and Jonas Brothers' Music From The 3D Concert Experience.
There's bound to be some debate over whether This Is It should be called a soundtrack. The album features studio (and a few demo) versions of the songs heard in the movie. The copy on the album cover is "the music that inspired the movie." The movie credits refer to it a "companion album" rather than a soundtrack. Nonetheless, Nielsen/SoundScan includes the album on its soundtrack chart. I, too, think it should be considered a soundtrack. The album has the same title and artwork as the movie poster and ads. It's not a soundtrack in the classic sense, but it's the closest thing to one that's available. If there were a chart for Top Movie Companion Albums, that would be the place for it. In the absense of that, we can call it a soundtrack.
Jackson long wanted to be a movie star, a sort of modern-day Fred Astaire. In death, he got at least part of his wish: a #1 box-office hit. This Is It topped the box-office in its opening weekend with a domestic gross of more than $23 million. Jackson is only the fifth music star in the last 25 years to star in a movie that came in #1 at the box-office and also spawned a #1 soundtrack (on which the star was featured). The others are Prince, with 1984's Purple Rain; Whitney Houston, with 1995's Waiting To Exhale; Will Smith, with 1997's Men In Black; and Eminem, with 2002's 8 Mile.