I am not really sure how to define it.
What I am looking for is ":| this looks amazing" and you spend so much time taking in the graphics you get killed/drive off the road and have to start again haha
With the Superman mod in Just Cause 2 I can spend an hour just flitting about just above the treetops checking out the scenery (and blasting the odd car away from 500ft above a road heh). I know the game looks very cartoony but the rainforests, water etc are very well done.
I found the graphics for Just Cause 2 very disappointing. It's actually the reason why I stopped play it somewhere in the middle.
Crysis is by far the most demanding, I guess it depends how you define "graphically pleasing" Far Cry was nice because it was different being set in the tropics or on a beach as opposed to AVP which is always dark but has good graphics