I started gaming in the early 80s so "older games" for me means 2D, smooth 60fps, and great and unique art styles. I have zero issues playing games from 1985-1995, that's the best era for me, especially the 90s arcade games. And SNES, I have no issues playing just about anything. I play through Super Metroid regularly, it's still awesome.
But yeah, PS1 and N64 games in general don't hold up well, 2D games are okay but most 3D games feels super janky and is badly optimized. PAL conversions were lackluster as well, 25fps as standard and black borders at the top and bottom. Ocarina of Time even went to record low 17fps as standard, unplayable for me even back in the days and today it's just complete trash, nostalgia is not enough to help out there.