In all honesty, I've become somewhat jaded to games. As a graphic artist the CGI never blows me away, from experince in collecting stories it's hard to completly wow me with that, and no gameplay has been so diffrent it changed how I looked at things.
Yet I still recall one thing that for all it's simplicity did blow me away with existance. The clouds and sky in Sonic Adventure for Dreamcast. Oh we had decent Skyboxes for a while in PC games, but this was a console and actualy looked "next gen" for a console.
Alas, that system was the last time I ever really felt "this is a huge step forward in gaming" rather then the current "it's really just more graphics and CPU" sense of growth.