XBox 360 all the way GTA was the reason ps3 was being bought now Xbox 360 has 2 reasons GTA and HALO! (ps3 never gettin halo)
Top 100 Best Selling Game Series of the 21st Century. Scroll to the 11 page. GTA tops it, followed by Halo. PS3 will come crashing without GTA. And also PS3 are getting bad reviews if you would see the thread I made in this section.
Another funny thing, Grand Turismo 3 is 3rd. It probably would have Grand Turismo 4, but that list ends in 2003 and 4 came in 2004. Forza wasn't as good as Grand Turismo (although it fixed alot of things Grand Turismo didn't have) but its a decent replacement.
Morrowind isnt in there. It was the game of the year for the xbox and sold a bazillion copies, but it was released for the Xbox in 2004 IIRC.