I think its probably the one with the most nostalgia for most people. Between all the Square and First Party games, it had a handful of gems.
I think PS1's library was better overall, more diversity among the quality.
I just want to point out; if anyone is thinking something like GBA or PSP: The ports should not count.
SNES was basically just the best Nintendo system and two generation ahead of everything else in terms of quality.
That is to say, it was better than Playsttion in 5th gen, Playstation and Xbox rivaled it in 6th gen and finally surpassed it in 7th but Nintendo has never reached that level again.