My first dedicated gaming system was the PS1, and in general I have no trouble going back to the sprites and chunky polygons of the mid-to-late 90s, whether on consoles or computers
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as long as I can upscale them to 1080P
Beyond that it gets a bit hit and miss- SNES and Mega Drive games look and sound fine to me and I've played plenty of 16 bit console games as an adult. On PC, I can enjoy 2D stuff like Sam & Max Hit the Road or the original X-Com but most early 3D, like the original System Shock, looks a bit too much like visual vomit.
Going to 8-bit, while the vast majority of NES games are too primitive to my eyes and ears, I have no problems with Game Boy/Game Boy Color games.
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(Well, at least the good ones, mostly made by Nintendo)
Is it just nostalgia because I had a GBC as a kid or is it because Game Boy games came later and had more developed visual aesthetics? 
My limit is probably the very late 80s
I know System Shock is a great game, but every time I look at the controls and the interface I just go
I don't have issues with a complex, text-heavy interface with lots of buttons on isometric turnbased 2D games but in a first person game it's a "no thanks"
I got System Shock 2 and the other Dark Engine games, Thief and Thief II, off GOG ages ago and loved all of them, but I just haven't been able to get myself to start the original. Now the remake's been out for like a year and I'll eventually probably just play that instead (since it looks like SS2)
shills annoyingly You should in fact try the remake instead then! The game does fuck ✨ it's about to get a major patch, and I can confirm the remake is one of the best games ever made.