I voted PS1.
I did so because even though none of my favorite RPGs are actually on PS1, the PS1 had more RPGs, I think, than any other system and many of them are solid. This goes doubly if you only play RPGs in English.
For example, I love Panzer Dragoon Saga/Azel on Saturn, but I wouldn't recommend the Saturn to people I know as an RPG system because it only has like...6 of them, or so, in English. It has some nice Japanese RPG releases though.
Same for PCE. Great RPG machine. Not for for people that don't play import RPGs.
The SNES had some f*cking GREAT RPGs, including Earthbound, FFVI, and Chrono Trigger, but those games are still doing for 1993 retail ($70) or higher now in good condition, plus there really aren't that many SNES RPGs in English. Probably only 5 or 6 I'd actually play nowadays.