That's what I would probably go with. Assassin's Creed is also stunning in places. MGS4 doesn't look all that outstanding from what I've seen.360 = Gears of War
PS3 = Uncharted
I think that gold... thing (if you've completed it you'll know what i mean) in uncharted is just stunning. Perfectly rendered.
Also, while the framerate and the actual game itself kinda suck, Lair is very stunning to look at in places.
Obvious 360 choices would be Gears and Bioshock. Also that zombie game impressed me (i forget the title) just because of the sheer number of zombies on screen at any one time with no noticeable framerate drops.
Dead Rising, although I wouldn't sa that is a great thing to show off graphics.
Don't forget Fight Night: Round 3, that looks pretty amazing also.
Yeah, the textures etc were low res, but as i say it was just the enormous number of zombies on screen at any one time that impressed me, showed that the GPU could kick out a hell of a lot of oomph.