I'm not a manga or chibi fan, but...

... Vanillaware's games are absolutely beautiful.

Yeah, some go full-tilt into sexualization, but...

... the artistry of the images redeem the subjects IMHO.

GrimGrimoire
Odin Sphere
Muramasa
Dragon's Crown

And it looks like the upcoming Unicorn's Overlord will be pretty amazing as well.

Terranigma & Secret of Mana come quickly to mind.

This thread made me think about older games, as far as pixelated games go I really liked most of Origin's sims like Wing Commander, Privateer and Strike Commander. Not the inflight stuff but the between missions where you talked to your wingman/base personel and such.

I also really like the look of Raptor: Call of the Shadows, it really nails that military-esque not too modern sci-fi look, had great backgrounds and enemies.

For tactical and strategy games we apparantly need to go to Spain because Commando's and Stronghold is where it's at.
Commando's had some of the best looking maps I've seen and you could hang any screenshot in a museum and no one would complain, just don't let any old lady restore them.

Well, and now your post made me think of "The Pawn" (1985) and "The Guild of Thieves" (1987).

I don't know if I would call them "aestthetically beautiful"...but beautiful they definitely were (and still are).

Star Trek: The Next Generation - A Final Unity. *VERY* beautiful artwork, original cast voice-overs, and great story. That is probably my most favorite game of all times. Second to that, Mafia Definitive Edition. I'm blown away by how great the graphics look, and how far computer graphics have come in the last 30 years.

And actually, if there was any game I wish GOG would buy the rights to and release, it would be that game. I'd love them long time.

The Myst, Bioshock and Dishonored Series, Ori and the blind forest/will of the wisps, Little Nightmares I and II, Cyberpunk 2077

While Dragon's Crown went full booby bouncing low-cut-outfit sorceress (and some maidens you have to rescue that are scantily clad), Odin Sphere isn't like that (one or two characters may have semi-revealing). Maybe a little simplified, but sprite limits would be a main factor. I am not sure i'd say chibi, but it does have a very artistic look/feel to it that isn't anywhere else.

Vanillaware just has a very unique look and feel. Very much animated 2D artwork done well. Do things with moving/stretching until it doesn't look right. I do wish for more games like it.

Space Engine allows one to embark on a journey through the stunning infinity of the Universe, where the only boundaries are the limits of your imagination. For me, and my astrogator, the ever-droll Robby the Robot, we're on a mission to locate Altair IV, with its Krell-inspired mind-projected virtual power source. Awesome!((--;))

Off the top of me head I'd say the first two Oddworld games, especially Abe's Exoddus. Just the backgrounds alone are some of the most aesthetically beautiful I've seen in any of the many videogames that I've ever played!

Witcher 3, Skyrim, Fallout 3, Metro 2033 and Last Light, Borderlands 2, Dragon's Dogma.

(I have expanded "beautiful" to also include games which may not fit the standard definition, but have a distinctive and consistent visual style which improves the entire game.)

There are so many good-looking games that it's hard to choose. Here's a selection, in order of release date:

Agony
It was graphically very impressive when it was released, and is still pretty even now. This is what real pixel art looks like. Unfortunately it's better as a work of art than as a game.

Unreal
The alien vistas are were breathtaking when the game was new. It doesn't hold a candle to modern graphics, but the art style will always be good. Sadly this game was cruelly murdered, so you can't buy it.

The Void
This game is made of art, and you're the artist.

Tormentum - Dark Sorrow
If you like H.R. Giger, you'll like this game. Apparently not well-known, since it doesn't even have a wish-list entry here on gog.

Gorogoa
I would happily hang this game on my wall.

Banner Saga, Banner Saga 2, Banner Saga 3
Forgotton Anne

It doesn't need one ;-)

https://www.gog.com/en/game/tormentum_dark_sorrow

There is a Flower Game flower (real wind colours)
a_castle_full_of_cats (minimalistic catfinder)
symphonia_2020 (music drives moves)
terra_lander (minimalistic gravity flyer)
superhot (minimalistic timeshooter)
game/huniepop (somehow it is aesthetic)
https://www.gog.com/en/ga
shelter games https://www.gog.com/en/games?developers=might-and-delight
there are many games my brain accepts as aesthetic... plenty already mentioned in this thread

I think the game world of Alice: Madness Returns was very beautiful. Before you get into the rusty, industrial areas at least.