This is a really tough question, because I think so many games are really beautiful.

I'll have to go with Super Mario Bros. 3, Donkey Kong Country, Okami, Twilight Princess, Yoshi's Island, No More Heroes, and

Out of This World (aka Another World, aka Outer World)

All the Metal Slug games are all gorgeous.  My favorite is 3:

Jet Set Radio

Odin Sphere 

Okami 

Breath of Fire V: Dragon Quarter 

Panzer Dragoon Saga 

And lots more...

I agree with the opening posts choice, Super Mario Galaxy certainly has a beautiful and charming feel.

I'm also a fan of Final Fantasy scenery. Balamb and Fishermans Horizon were places I liked in FFVIII. (sorry, I have no pics)

Well like i was who posted wind waker pics, i have to defense myself. Maybe there are games better than wind waker, but, i havent played them, so, i cant give my point of view or say than they are better.

But, i see than you mentioned JSRF, i complete forgot it, i belive than its as good as wind waker. I player through the main story 3 or 4 times, but i never could have the 100% of the game :( I think i have to post some pics. And yes, it is a BEAUTIFULL game

this game is a pixar movie in a game!! everything is beautiful-

Since there hasn't been any love for Twilight Princess.

Okami, so beautiful. But I just couldn't push myself beat it.

Back in PS2 days, ICO impressed me a lot, and I did finish it.

Panzer Dragoon Orta, Otogi 1 and 2, and Ninja Gaiden on Xbox.

But my most beautiful game is a game I haven't played: Prince of Persia. Those screenshots are simply gorgeous. I have some backlog to finish first.

Hmm, I'd have to say Odin Sphere (hated the game, loved how it looked) or Eternal Sonata. Both look absolutely amazing.

Slightly long in the tooth tho I am
The games that first had me openmouthed on systems through the ages.

ZX Spectrum - Lightforce - no colour clash how did they do it ?
Atari 2600 - Starmaster - Xmas 1984 was just a blur.
Amiga - Shadow of the Beast - Parralax scrolling anyone ?
PC - Quake2 when I first used a Open GL Card - Stopped playing started gawping
Megadrive - Sonic - Colour everywhere and very quick hardware scrolling.
DreamCast - Virtua Tennis - You could recognise the players most of the time.
N64 - Super Mario World - To my mind the biggest single leap in gaming of all generations not just graphically.
GC - Resident Evil remake and RE4 - Pure genius
PS1 - Ridge Racer - The system lived up to the Dino Demo.
PS2 - God of War - I bought a PS2 for this and its sequel.
Xbox 360 - BioShock and Dead Rising. Still love em both
PS3 - GT5 prologue - Real pretty hope the full game is as good and actually models damage
Wii - Super Mario Galaxy - Cute as a button and no graphics slouch.

I wanna see pics of mgs4 in this thread!