Five games were nominated by the Writers Guild of America for the award of "Best Video Game Writing". Only one could win. And no, it wasn't Modern Warfare 2.
Even though Activision's shooter was nominated (perhaps based on the quantity rather than quality of the game's writing), along with Assassin's Creed II... X-Men Origins and... Wet, the winner was of course Uncharted 2, and specifically, writer Amy Hennig.