Crysis, if you play this on a War PC, with highest details. In AG the choice is very difficult, because some games have the same kind of graphic. Anyway i like very much the graphic of Tainted Kingdoms (that is as Sonny).
I'd have to say Grand Thrift Auto 4. Not because others are saying that but because it's a whole world that you can explore, and that everything seems so real. Unless you go through like 3 holes where you fall... I found them :P
graphics almost dont matter to me at all. for the best graphic though id say final fantasy 10 (in the cut scenes of course).
but honestly if there is one game that i really enjoyed the graphics in its okami. it had such an original beautiful graphic. even if your not going to play this game i really recoment to just watch alittle on youtube just to see the special graphic