Uncharted.

Haven't we had like a ton of these threads before? :p
Anyway, it really depends on what you would call 'best' graphics. In the end it all comes down to personal preference.

i can't choose out of gears, uncharted, and gran turismo 5. they all use the visuals differently, but effectively.

For me Bioshock creates the best world of any game I have played so far. Some of the graphics in that game (Albeit fairly close quarters) are just incredible.

"Best graphics" is always a cliche, smaller environment games (GoW, Bioshock) can fit more detail in than larger environment games (COD4, Uncharted).

I think GTA4 also deserves a mention for just the sheer size and variety of its graphics. I havent played either yet but, for racers, GRiD and GT5: Prologue are supposed to look superb.

BioShock, Super Mario Galaxy, Assassin's Creed, Lost Winds

BioShock created an environment. Rapture was beautiful.

Graphics? Not so much. Smoke and mirrors if you're not including PC (which Crysis would take hands-down).

On the 360 alone, Gears was more impressive graphically. 

 Graphics , not art direction , Wii games shoudln't even be mentioned on this thread.(IMO)

GT5 and Uncharted are amongst the best i've seen. 

Uncharted is visually magnificent....

But what about Assassins Creed? Some of the sights in that game blow the mind...