i just finished plating the COD 5 was better then the cod 4 .. i highly recommend you to play that.. even prince of Persia is going to be released waiting for it
I recommend Crackdown, which is basically a game like GTA, but you are the Establishment so all the stuff that got you stars in GTA is a good thing, such as taking people out, blowing up cars and such. Also has an interesting art style, and is extremely fun to play for a few minutes, or even a few hours depending on how much time you have to play.
Gears of War 3, Battlefield 3 and Need for Speed: On the Run are some new games to be released in near future. They are supposed to be really good and exciting.
A lot of people are going to/have said this. But the CoD series cannot go wrong. I recently picked up MW3 and the campaign was brilliant. The ending, for me was a bit anti-climactical because I expected something different (which I wont state for spoilers etc). But overall the game is brilliant.
Online Mode at the moment is a bit frustrating because people are still getting used to the game/maps. But hey, give it 2-3 months it'll be an updated CoD4!