For visuals, I tend to think "pushing console limits," whereas art direction in my opinion tends to be what the best way to present something without necessarily pushing those limits is.
So here are my picks for visuals (remember, I have to played at least part of these games once):
Only played MGS4 once, but it looked amazing.
Only played Uncharted 2 at a kiosk, but it looked amazing
And Killzone 2 is about the only FPS I've really enjoyed playing in some time, due mostly to the graphics and the nail gun.
As for Best Art Direction? Pretty much any cel-shaded games I've played, ESPECIALLY... WAIT FOR IT
Wind Waker's art direction effectively turned Zelda into an interactive Disney movie and it was awesome.
They might both use cel-shading, but Okami is definitely more Japanese water painting than Disney anything like the Zelda title. Definitely thinking of picking up Okamiden after playing this at a friend's on Wii.
The Warner Bros. to the Wind Waker's Disney, Sly Cooper's style was perfect for its humor and storytelling.
And let's not forget the brilliance of making a game based on spray painting look like a moving spray painting.
And of course 2D fighters like
Guilty Gear X2 had awesome graphics even if it wasn't 3D like most PS2 games
Of course where Guilty Gear had amazing busy backgrounds, SF3 had static backgrounds but really fluid and detailed characters
And just for fun, a game from my childhood that has become obscure:
Hope you all have a great day. I'll continue posting blogs, but if they diminish in quality it's probably because I'm hungover