What are the most aesthetically beautiful games you have played?

Okami comes first to mind with a world that lives and breathes on the brush strokes of calligraphy.

The Little Acre
Shadow of the Colossus
Skullgirls
Street Fighter 3
Tokyo 42

I really like the forest areas of Secret of Mana (of which there are plenty) and Chrono Trigger (of which there aren't enough).

Paper Mario The Origami King

The Trine series.

In no particular order:
- Okami (because of the Calligraphy aesthetics)
- Super Paper Mario (because of the "paper cut outs" aesthetics)
- Dishonored (I'm not kidding. Back, when I played that for the first time, I was enamoured by the art. You can see the individual brush strokes on the assets - it's beautiful)

Shadow Warrior 2013

Crysis

Trine

Super Mario World 2: Yoshi's Island

Maybe not easthetically the best but there was something about playing Stalker that kept me playing.
The world you play in felt authentic and not gamey like most other games, which perhaps is an achievement on its own.

When it came out I thought Elite Dangerous was very pretty, but I guess with time less so.
Lack of asset diveristy and that for some reason the devs really like the color of orange was one of the reasons I gave up on it. On the other side of the spectrum there is X2, which I'm playing at the moment, the graphics still look very good in my oppinion.

At first glance it may not look like it but I think Anachronox has a very good easthetic (for a Quake 2 engine game), very diverse universe with interesting locations far from the formulaic humdrum of most games and still some of the greatest cutscenes in gaming.

Ghost of a Tale is the first that comes to mind. It's just stunningly beautiful. It's a world I could get lost in for hours.

The Trine games are also fantastic. They absolutely nail the fairy tale aesthetic. Even Trine 3, for all it's faults, is wonderful to experience for its visuals.

Apotheon has one of the most unique looks I can think of, and it's not just style without substance. It's absolutely crucial to the immersive mood the game builds superbly well.

Well, I never had computers that could play games focusing on graphics, at least not until many years after release, but at least in terms of attention given to artistic detail, King's Bounty: The Legend (for all the little animations and details, mainly environmental, that you may even miss if you're not paying attention), King of Dragon Pass and Jotun come to mind.

Child of Eden, for Xbox360
Odin Sphere

Dragon Quest 6 (SFC version) is also beautiful, along with Dragon Quest 3 (SFC remake).

Dust: An Elysian Tail. It's aesthetically beautiful because the whole game was hand-drawn by a guy who is a professional cartoon artist & animator as his normal job, and a game dev only as his occasional side job.

Assassin's Creed IV: Black Flag. It's not only aesthetically beautiful, but also easily the very best AC game ever made IMO (no wonder, then, why GOG doesn't have it and probably never will :( ).

Streets of Rage 4 is aesthetically beautiful in terms of the color palettes that it uses, but not necessarily in terms of the characters themselves.

King's Bounty: The Legend. It's both aesthetically beautiful and aurally beautiful at the same time.

Mafia (2002): But the GOG version isn't worth playing unless you know how to un-butcher it with an unofficial mod.

Some people are listing horror games. If we are including horror as "aesthetically beautiful," then I also have to say Nocturne (1999), which has the most fantastic horror aesthetics I've ever seen in any game, and which could be considered beautiful from a horror standpoint.

A close runner-up in that regard would be Dying Light 1, which also has beautiful aesthetics, from a horror standpoint.

Likewise also with Painkiller: Black Edition.

And, all three Dark Souls games are also aesthetically beautiful from a horror standpoint.

It does, yeah. But that engine also makes it... move too smoothly, for lack of a better term, which makes those sequences feel odd, and I heard of people say they were even nauseating.

And since you mentioned a space game, also thought that Homeworld 2 looked about as good as a space game could need to. But you don't really see it, staying mostly in the tactical view. Or at least I did.