I'd say its a draw between GoW3 and U2 at the moment. Both have amazing engines, pump out colour, textures, etc. to a crazy degree and contain some amazing animation and seem able to robustly support multiple gameplay scenarios.
Killzone 2 would be just behind then probably Gears 2.
Overall, if I had to pick one I'd probably take Uncharted 2 as GoW3 did have some rough edges whereas vs the almost alarming level of polish in U2. The animation and character models in many of the cut-scenes were noticably weaker and (while perhaps more due to staying true to the franchise) Kratos animation is bizzare - his walk and double jump are just awful but when running/fighting it's very good apart from the obvious 'snap' between animations vs the wonderful blending technique used in U2.
I also think LittleBig Planet is amazing visually - and its amazing textures, which leave pretty much every game including GoW3 and U2 in its dust, don't get enough praise.
Flower also amazes me personally with it's grass animations.
Try to be reasonable... its easier than you think...
