PS1 texture warping (due to a lack of floating point precision I believe?) caused walls to really jitter and shake and it is... a really nauseating effect.
Fixed perspective games like Crash and Final Fantasy seemed to have less of this from what I remember, but games where you could come close to the wall and the camera could move in a bunch of ways just look so rough now.
Kind of really glad for the remaster of Spyro and I hope Ape Escape 4 comes soon so I don't have to go back to play the PS1 game to satisfy my Ape Escape desire (don't own the PS2 games).