As of August 8th, Halo 3 has become the first Xbox title (both original and 360) to sell over 10 million copies. Of course if you’re reading this blog you probably won’t be very surprised. Halo 3 had excellent reviews and the original halo was instrumental in building up the popularity of the Xbox Live network. The game opened to over 3 million sales in just its first week alone and even now, after 2 years, it still commands a respectable 30,000 sales weekly. In fact, the only reason some analysts are projecting slower sales in the near future is due to the release of Halo 3: ODST.
BTW: Halo 3 is the latest of only 35 games in all of history to sell over 10 million copies; the number 1 being Wii Sports which straddles atop the list at an astounding 45+ million copies sold.

[Source: VGChartz]