@Onyxmeth

Far Cry Vengeance is the Wii franchise's port?

At whoever asked....
I own Resident Evil 4 and God of War 2, and I easily pick RE4
God of War looks so nice because it's often zoomed out and in a set perspective.
Resident Evil 4 is up and in your face and still looks incredible.

 If we add in prerendered, definitely REmake/RE 0. Kotor had awesome environments, Wind Waker and Okami win for artistic kick-assery.

I think Halo Combat Evolved was technically impressive, even more so than its succesor in many ways. Great lighting effects, bump mapping, the sheer amount of action (multiple enemies, explosions), expansive environments, speech, outstanding AI (I know, not gfx, but still technically impressive), the minute detail when you zoomed in close to objects with the sniper rifle, and the fact that dead bodies and weapons did not disappear like nearly every other game, were collectively, quite an achievement at the time. I recall the PC version, which despite being released a couple of years later, was still very demanding for high end gaming rigs.

God of War 2!

I really like water effects. (And the cube had the best last generation.)

That's why I choose Waverace: Blue Storm.

I'm not sure what was the best looking game, but i can tell you it was not on the Gamecube or Playstation2.

For me personally:

Zelda The Windwaker.

The Chronicles of Riddick: Escape from Butcher's bay.

Resident Evil 4.

Ninja Gaiden.

Zelda Twilight Princess.

Rogue Squadron games (part II and III for Gamecube).

Okami.

Overall, Xbox might have had the technical edge, but Nintendo's system has te best looking games i.m.o because of the variety and the use of the Gamecube's power to push it to the edge! 

Zelda: Windwaker is still the most beautiful game ever created for me. The art style and vividness of the graphics were amazing.

FF12, Okami, REmake and RE4 are worthy mentions as well.

For pure stylised beauty what about Rez, obviously not technically but the art direction is amazing. Okami and Riddick are up there as well

What about Shenmue?

Graphically astounding...coming out in 1999/2000. Had brilliant graphics, animation and was a great living breathing world, that had time-based lighting. Yes there were other games that probably looked better, but for being an 8 year old game, it just looks brilliant.