Best Xbox games under 50 bucks

I've been feeling up for a new game recently and I can't settle my mind on what 360 game I should get. Prototype is a maybe. What do you suggest?

The best deal is probably Batman AA

L4D2 is 39.99 in CND.

Gears Of War 2

Mass Effect

Dead Space

Did you happen to see the Sticky way up there? The really big one? If not, would you like a link? There you go, a link.

Crackdown

Dead Rising

Gears of War

Call of Duty 2

Yes I have, no price tags :D