Um...
The Bourne Conspiracy
Deus Ex: Human Revolution
Need for Speed - The Run
Mafia 2
Splinter Cell - Conviction
Lost Planet 2
Rainbow Six - Vegas 2

Personally, I'd add Split/Second to the list.

Warhammer 40000 - Dawn of War 2

"Would you let your kids play M rated games?"

Yes.

Wait, so what's the best looking game on XBOX 360? Is it Rage or Battlefield 3???

Mafia 2 has one of the best stories I have ever seen in a game. Bulletstorm has kind of a fun story. Then about every Call of Duty game since COD4 has a great story. And I would add The Chronicles of Riddick - Assault on Dark Athena to that list aswell.

Let me tell you what's ironic:
Rain on your wedding day.
A free ride, when you've already paid.
Good advice, that you just didn't take.
A traffic jam when you're already late.
When a man buys a shotgun to keep himself safe but drops it and it somehow shoots him in the face and kills him.

BuriedGirl

Many I haven't played yet but so far:

1.LA Noire
2.Deus Ex: Human Revolution
3.Bulletstorm

Probably not final, though. I'm expecting Need for Speed - The Run, Call of Duty - Modern Warfare 3 or Saints Row: The Third to take 3rd place.