If multiplatform games can count, a possible further contender for this title (ok not the title as Mario Kart will definately keep that, but passing GTA:SA) is actually Call of Duty: World at War.
Call of Duty 4 after 52 weeks sold 10,369,634 copies across X360, PS3 and DS.
After 6 weeks of sales CoD: Waw is 2,119,588 ahead of what CoD4 was at after 6 weeks (2 additional platforms of Wii and PS2 helping a little, but most of the extra boost came from increases for the PS3 and 360 versions)
If it can keep that lead over it's older brother, WaW would have sales of around 12.5 million after 52 weeks..... GTA:SA on PS2 had about 12.15 million after 52 weeks, so the question is, could XB sales have been as low as 350k after 4 months, I say unlikely, but if CoD: WaW keeps increasing over CoD4 it might have an even bigger lead after 52 weeks.
