I really enjoyed God of War 3 but I must say Uncharted 2 wins out pretty easily for me.
Both have among the best home console graphics out there. GoW's sense of scale is truly epic and the character detail is stunning. However the graphics in Uncharted 2 are just more polished to me and run smoother to boot (love the animation).
If you compare the writing, and especially, the voice acting, Uncharted wins hands down. All of the actors in U2 are top-notch, while GoW shines with some characters (Hephaestus and Hermes are among my favorites), but many others, like Kratos himself, are poor IMO (liked his voice acting just fine in the other games, just not part 3), and some are truly pathetic, such as Hades.
GoW3 starts out stronger though (the first level is a perfect 10!), while U2 didn't really start to blow me away until Borneo, but after that U2 never disappointed me (the last battle is a little weak, though), while GoW ranges from excellent (the Helios and Cronos levels especially) to a bit mundane.
Overall Uncharted 2 is just more interesting, has better control and is a more polished experience. God of War 3 is a great game while Uncharted 2 is truly a rare gem.
