1. SNES - Final Fantasy IV and VI, Chrono Trigger, Secret of Mana, Earthbound, and others I know I'm forgetting. whatever the case, two fo the best RPG's ever made--FFVI and Chrono Trigger-- were for the system.
2. Right now, neither really. I would give the DS the edge only because it can play FFIV and FFVI for the GBA but other than that, there's nothing original and impressive on either (and I even count FFIII as original). That might change when the remake of FFIV is released, but we'll see.
As for the countless remakes of FFI and FFII on the PSP: FFI and FFII are bad games. Good for their day, but they haven't stood the test of time. About the only reason to play FFI is for pure nostalgic reasons and nothing else.
3. There use to be countless RPG's on the PC, only they were called point and click adventures. Sadly, that genre died (though hopefully it's going to make its long awaited comeback).
4. no one console is really better for an RPG than any other. I suppose handhelds are my personal favorite because I like being able to take them with me when traveling, doing mundane tasks, and so forth.
