PS1 and N64 visuals have both aged poorly, though I agree, I think the PS1 is the toughest to go back to from a visual perspective. The shimmering polygons that you see on the PlayStation and on the Saturn feels unacceptable by today’s standards and then they are both also notorious for long load times.
The N64 has it’s own set of graphical limitations, but hold up a bit better to the test of time, IMO. At the time I know it was the school yard debate of which looked better and many felt the sharpness of the PS1 was preferred over the softer N64 image.
Weirdly, I think sharpness is exactly where PS1 games don't hold up. Metal Gear Solid is less off-putting to go back to than Metal Gear Solid 2. The pixely textures and dim lighting give it some atmosphere, where the extra detail in MGS2 just comes off as very plastic now.
The N64 has it’s own set of graphical limitations, but hold up a bit better to the test of time, IMO. At the time I know it was the school yard debate of which looked better and many felt the sharpness of the PS1 was preferred over the softer N64 image.