I personally got a PSP for the awesome modding possibilities, which would enlarge your collection to all of the Playstation and SNES titles, but also to other emulated consoles.
If you're only planning to buy original games, however:
-Breath of Fire III
-Final Fantasy Tactics: War of the Lions
-Parappa the Rapper (that's a strange game, I know)
-Valkyrie Profile

I just realized all of these titles are remakes of PSX games.