1. Halo 2 - 8 Million copies sold
Released in 2004 as a successor to Halo: Combat Evolved it was a huge hit and is the best selling Xbox game with 8 Million Copies sold.
2. Halo: Combat evolved - 5 Million copies sold
Released in 2001 with the Xbox it launched the successful franchise that is Halo.
3. Tom Clancy's Splinter Cell - 3 Million Copies sold
Released in 2002 this stealthy shooter was an instant hit upon release.
4. Fable - 3 Million copies Sold
Released in 2004 this too was an instant hit upon release.
5. Project Gotham Racing - 2.5 Million copies sold
Released in 2001 this is the best selling racing game on Xbox.