PS3
Uncharted 2 - everything (Gow III ins't in the same league)
Killzone 2 (and maybe Killzone 3) - for some amazing particles and animations
Flowers - artistically and 1080p
WipEout HD - 1080P (1920/1240) and 60 FPS
A Crack in Time - amazing looking game running with very high frame-rate , despite low overall resolution.
Xbox 360
Red Dead Redemption - miles better than PS3 version. I can't believe how this game works so well on 360.
GOW2 (and maybe third part) - solid game all around. From models, to textures and stable 30 FPS in real 720p. The only issue that i have with Epics game is flat lighting model they use.
Bajno - Why Microsoft, why? On of the most technically capable developers make mostly avatar's stuff and Kinect bullshit?
Resident Evil 5 - again, PS3 version pales in comparison - textures, lighting, missing effect, low frame rate. For me 360 version is small technological marvel.
Also, i want to see what can Naughty Dog do after amazing optimization for UC2.
Halo Reach is also quite interesting from a technical perspective.
New Insomniac game for EA. Crysis 2 from Crytec, along with this exclusive game they announce for 360 at E3.
But my personal winner for optimization and overall tech achievements is Uncharted 2.
Cheers from Bulgaria