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 think historical-materialist forces cause an evolution of an artform that make earlier forms less accessible. For example, only the hardest-core movie buffs watch films from the Silent Era. The same forces affect video games.
It's no secret that earlier games are simpler, both graphically and gameplay. Games are simulations. When earlier computers were less capable, fewer things could be simulated the game. It's not like earlier game developers didn't have grandiose ideas about what they wanted (see: Dungeons and Dragons), but those limitations means only the absolutely necessary make it into the game. Many games of the 80s and 90s came with a manual because they could not fit all the descriptions/tutorials/story within the game executable itself. It also meant that affordances from later games are conspicuously absent, and can make going back in time a frustrating experience. On the flipside those limitations also made games paradoxically easier to make. When you accept the technical limitations and don't try to achieve beyond them you get endless franchise-powered games, like Disney movies or games-as-vehicles-for-toys. Go back far enough and you get Atari shovelware was put out faster than the Steam store, resulting in a collapse of the US video game market in 1983. As games became more complex (graphically, gameplay, etc), and thus more expensive to make, it became harder for franchise-vehicle quick-buck games to sell.
That being said, there's something about an artist that takes the limitations of their medium and works through it. Charlie Chaplin films are still fun to watch despite the limitations of their time. You can appreciate a game's "Art History", coming to understand the evolution to where games are today by how previous artists worked (and failed) in the past.
tl;dr: It's not just you. Games are better than ever now.
I just wonder if it's a simple generational thing where whatever you grow up with becomes the baseline compared to which anything older looks increasingly primitive and impenetrable or if video games achieved a level of graphical fidelity and game design sophistication at some point that would make them accessible even to new audiences.
I would imagine it'd be easier for a person born in 2007 to go back to Final Fantasy 10 than it would be for a person born in 1992 to go back to Final Fantasy 1
Final Fantasy 7 is a great example. The original game is a classic, but it does have some infuriating gameplay at times and the graphics are definitely early-3D vintage. Try climbing the Shin-Ra tower and try not to get frustrated! The remake sought to carry forward the good ideas (story, Materia), ditching things that are dated (time/turn-based combat, random encounters), and adding newer designs that came after it was released. The Godfather is a movie equivalent to FF7. Easily a classic, extremely well done, and looms large on the history of film. However, these days we learned many film techniques from that movie and others. while at the same time the high praise also creates high expectations. The Godfather has difficulty standing up to it's lofty scrutiny these days simply because our tastes and film-making abilities have increased as well.
Art forms evolve by learning from previous artists, and art consumers evolve alongside.
It's crazy how big the graphical gap is between 7 and 8. Not just in terms of the ingame character models but the quality of the pre-rendered backgrounds and cutscenes. Compare any cutscene from FF7 to the opening movie of FF8 and it looks like a generational leap.
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Too bad the actual game kinda sucks
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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.
Chaplin made silent movies long after the sound film had been invented. He was very vocal about his dislike of "talkies" and saw them as . Chaplin saw in silent cinema absolutely no limitation that'd have prevented him from making the films he wanted to make. While adding sound to films seems like obvious progress to us nowadays, it also further diluted what made movies unique compared to other artforms. There's no reason to think we couldn't have had a hundred years of incredible, inventive and still surprising silent films. Books haven't changed in thousands of years and they haven't started repeating themselves yet.
Technical and artistic progress aren't connected in any straightforward manner. The topic of course gets quite a bit more complex for videogames since they are so deeply interlinked with consumer technology and are more directly interactive than other media, but the vast majority of videogames made today could have been made twenty years ago as well. The actual reason people usually don't play older games is because the one thing that we've actually seen undoubtable progress in is that games have gotten much more effective at keeping your dopamine receptors firing. If you grew up playing ubisoft games or mobile gacha bullshit you'll find it very hard to enjoy games that might delay gratification at all (be it through deliberate means like difficulty or non-deliberate like bad tutorials).