Beauty is, I think, somewhat in the eye of the beholder. A few games that couldn't have been called very conventionally pretty, though:

A number of roguelikes that use ASCII graphics (though today I play Cataclysm: Dark Days Ahead* in graphics mode). Same for Dwarf Fortress. Often these are very deep games with a lot of gameplay to explore and a lot of replayability but nobody is playing them because of their graphical beauty.
The Dominions series and Conquest of Elysium series from Illwinter are fairly-involved strategy games, which both have graphics that...well, I can understand someone appreciating some aspects of them, but again, nobody is buying these games for the graphics.
Kenshi -- a squad-based open-world sandbox game -- has a certain amount of attractiveness, but the textures and models are limited in detail and I don't think that people are going to call its graphics beautiful or on-par with high-budget games today.
Noita is a difficult action roguelite game where one constructs wands using various spells and spell modifiers and gives one's wizards various powers as they dig through a world. The graphics are pretty chunky pixel stuff, which someone can enjoy but aren't something that you'd probably play the game just to look at.

I think that the importance of graphics is more-important for games that don't have a lot of replayability. There's a lot of "oh, wow" factor when you see something beautiful and it's still novel. But if you see something many, many times, eh, less-impressive. A lot of roguelikes and roguelites focus on replayability -- the graphics of something that you've seen countless times are going to be old hat at some point, no matter how pretty.