What Are Some Good $20.00 Xbox 360 games?

I'm kind of leaning on Dead Space, but what are some other games that are currently $20.00 that are worth playing? I didn't enjoy Assassin's Creed, so that one is a no-go.

Have a look at Amazon.com there having a sale. there are lots of great games. Dead space it a very very good game. I think assassin's creed 2 in the amazon sale.

Mass Effect / Orange Box

Dead Rising.