What games do you think had some stunning art behind it?

[Nemoide]

I've always found the Panzer Dragoon series to have one of the most interesting aesthetic senses for a video game.

[Bradtemple87]

Most 2d fighting games come to mind for me

[Reprise]

I've always found the Panzer Dragoon series to have one of the most interesting aesthetic senses for a video game.

I also was going to mention the Panzer Dragoon series.

Other games that come to mind:

Killer 7 - This game has an awesome art style to it, a very unique and weird game.
Shadow of the Colossus - like many have said
Shenmue 1 and 2 - Visually, it's not as realistic as it wants to be. At least now when you look at it. But the amount of detail and beautifully constructed characters and scenery make it gorgeous.
Rez - I know it's simplistic in nature, but I love the style and direction of this game.
Jet Set Radio - the cel shaded graphics blew me away at the time, the art style and 'graffiti style' is awesome.

[Key-Glyph]

Those old Lucas Arts SCUMM adventure games had to have a lot of art behind them.

They were my first thought too! I love well-done blocky pixellation. I think it's harder than it looks to pull that off with style.

I also remember being mesmerized by the lushness of The Lion King for the Sega Genesis.

[Michi]

Some really nice choices so far. I'm a real fan of the cel-shaded look, so the first things I think about are:

Wind Waker
No More Heroes
XIII

I was also impressed with:
Fragile Dreams
Madworld
And the Resident Evil Remake.

[ZenLogikos]

Prince of Persia (2008)
Bayonetta
Outland
Limbo
Hard Corps: Uprising
ilomilo
Alan Wake
Winterbottom
Lucidity
Mushihimesama Futari
Bionic Commando: Rearmed

[BoringSupreez]

Limbo

For sure.

[Yancakes]

The first game that came to mind was Comix Zone. The art and the music are both awesome in that game.

Heck yes. I love everything about this game.

Metal Slug series have fantastic backgrounds an animation.

I really like Pleiads (arcade), and Defender, which to this day has the best lazer effect ever.

[Blurz]

The Sly Cooper games

This is one of few games where cel-shading is used to enhance the game's presentation.

[sheath]

Shinobi III and Ninja Spirit have always struck me as well drawn games. I particularly like the "Traps" level in Shinobi III with the moon in the background while you jump UP a bunch of falling boulders. Level 2 in Ninja Spirit also has an awesome huge crescent moon in the background.

Actually, come to think of it, the moon in the first level of Revenge of Shinobi always made me want to stop playing and stare at it. The waterfall in RoS's second level remains the most beautiful waterfall I have ever seen in a game to this day.

I also appreciate the little details in all three of these games, from fences to bosses everything is just really well drawn and puts me in the setting perfectly.