Simple really, what game looks best according to you? 
But this isn't some "GOW3 is teh best looking console game!", "na ah, its Uncharted 2!", "lawl, Crysis >>>>>>>>>>>> any console game"-thread. It's a thread about beauty in videogames, screw technology! If you think Battletoads is the prettiest game you've ever laid eyes on, more power to you!
For me, I think the most beatiful game is Guild Wars 2. It's not particularly high tech, but it oozes style and beauty no matter where you look.
Runner-ups include:
Valkyria Chronicles (great style)
Critter Crunch (amazing art!)
Mirror's Edge (amazing style, superb use of color)
Uncharted 2: Among Thieves (technology or not, it's still one beautiful game)
EDIT: I better include Flower to embarrass myself less!
And many others
