Well if u mean the best selling exclusive game on 2011, just counting the units sold during that year, i'd say
LittleBigPlanet 2 - 3.M
Zelda - 4M (but it'll depend on launch date)
Gear of War 3 - 4.5M
If u mean best selling exclusive game based on LTD figures, i'd say
Uncharted 3 - 5.5M
Zelda - 7M
Gears of War 3 - 5.8
<a href="http://exophase.com/gamercards/"><img src="http://gamercards.exophase.com/60143.png"></a>