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)
My limit is probably the very late 80s
Maybe for some people but I started gaming on DOS and NES and for the most part I dislike old games. I have tons of nostalgia for stuff like Myst and Golden Eye but going back to play them is just not fun. A part of my problem might be that I get motion sick and old games can be really bad for that. Original NES games can still be fun, super mario 3 will remain one of the best games ever made.