Many of us are very tolerant of old games, else we wouldn't even have gone here in the first place. But even still, there's a line drawn in that metaphorical sand where one might go, "Nah, I'm good." in regards to graphical prowess and gameplay.

As for me? In terms of 3D polygons: You want me to look at those monochrome cones and tell me they're trees? Okay.

But in terms of 2D graphics, I find it hard to go back much further than the Famicom/NES/Master System/MKIII. Especially when your accompaniment was either crunchy noise, dead silence, or a screeching flaming calliope. (TIA/POKEY)

On the other hand, I used to play Jetset and JumpJet, both of which feature practically nonexistant sound and graphics, so it swings in roundabouts.

My cutoff point would not be a lower end, but more a higher end. When graphics get past a certain point, it can sometimes be harder to tell what's going on than with older graphics that are simpler and cleaner.

As a result, I don't really have a lower cut-off point, but I may have a higher one, which might coincide with games going 3D, or even 2D games that are busier, or that use isometric (rather than overhead) perspective. I note that, for example, it's harder to tell what's going on in a game like Baldur's Gate than in a game like Ultima 4, for example. (Although that's not the only reason for that difference; Baldur's Gate's use of real-time-with-pause is not good for following what's going on.)

Anything with audio that sounds like a dot matrix printer is where I get off.

Anything that looks worse than HOMM 3, then I can't be bothered.

I've lost a tolerance for the entire DOS interface, they're so painfully slow and awkward to navigate that I just don't bother anymore.

I find the basic, garish color palette of some late 80's - early 90's games to be too much for me. But then I also dislike games that near photo-realism (for the same reason I tend to dislike VR).

One makes me wince, the other makes me uneasy.

But probably the only games I wouldn't play are those I grew up with -- text adventures. I just don't have the patience to read an entire game.

This is a bit more difficult. I'd say NES or 8bit games would be my limit for 2D or sprite games, childhood Atari800 games come to mind. Beyond going back to those, i'd say 16bit consoles for the most part.

3D? Hmmm.... I hesitate to suggest i'd try some PS1 titles again, the janky 3D and no Zbuffer. Dreamcast/PS2/Saturn is likely my 3D limit on graphical ability/quality.

So everything from the C/PM machines to Dosbox?

At the lower end of things, probably well done NES-era graphic are the minimum I tend to accept. Anything SNES and above looks good to me.

For 3D, some of the early 3D graphics feel very so so to me now (anything that seems too blocky or flat, unless it is done with a purpose for artistic flair... we've just seen a lot better).

For some kinds of games (like turn-based strategy), unless it is done extremely well, I just prefer 2D over 3D.

Also, it will probably be blasphemy for AAA aficionados, but to me, for about 8 years now I'd say, I've had an increasingly hard time noticing the degree of yearly improvements in cutting edge graphics. I think we're getting rapidly diminishing returns here. The human eye can only notice so much.

Nowadays, I tend to get the most excited about graphics that push artistic boundaries, rather than graphics that look ultra realistic. I was more excited about the visuals for this game, than the visuals for any AAA game: https://www.gog.com/en/game/bleak_sword_dx

I've probably never heard of C/PM, so thanks for the warning.

And the wobbliness of PS1 games actually makes me subtly sick. The poor thing can't process a few polygons moving together as a camera moves through a small room.

Control Program/Monitor. One of the original co-hosts of the Computer Chronicles was the creator of it. (So CP/M, my mistake.)

I would say Fallout 1 and Wolfenstein 3D is as old as I can go. Some kind of 16/8-bit side scroller stuff is too old for me.
I can play any low-poly 3D game though.

Emulation has managed to fix that, though.

I don't do DOS games older than the 90s, as all other systems had better quality. It's pretty sad that most of the really old games on GOG are the garbage DOS ports; even the original Mac with the B&W graphics was preferable to the garish 4-color CGA mess and ear-offending beeps of DOS, to say nothing of the much better Amiga versions. Even the C64 was better.

Don't get me wrong, Mario is a great Game, so is Resident Evil,
but I gave those days up in 2020 & don't want to go back to them,
i'd like to keep playing Games like PS3 Era Up to Elden Ring Launch
if I can, but most of today's games are not very good, & people put
Diversity & Equality over Quality of Game, & these Games end up bad.

So i'm not sure if I want to continue buying Newer Games.
I came from Steam after some Steam related issues, &
figured i'd give GOG a try.

Wolfenstine Enemy Territory has already been a joy for me,
but it's no battlefield Game, so it'll take getting used to. =D

It depends on the genre. Silent monochrome DOS text adventures are as basic as graphics / sound gets yet I'm fine with some of them. I'm also fine with replaying many 8-bit ZX Spectrum games. I have skipped a few titles from that 'awkward era' though where 2D transitioned to 3D with some painful 'learning experiences' (eg, tank controls and bad / jumpy camera angles in point & click adventure games) as well as a few 'PC Speaker' DOS games that actually sound painful to listen to. Some FMV games have also aged more gracefully than others.