He said PSX (meaning PS1), not PS2. Both Dark Cloud games and Disgaea are on PS2.

Here are a few suggestions for good PS1 RPGs besides the FF games:

Chrono Trigger (Pick up Final Fantasy Chronicles, it's a CT/FF4 two-pack)
Chrono Cross
Legend of Dragoon
Legend of Mana (don't listen to Medieval Bob, it's an awesome game)
Xenogears

If you want a long game, grab Legend of Dragoon. It's a pretty standard RPG, but it's fun and it's really lengthy.

If you're looking for something not quite as long, pick up FF Chronicles (for Chrono Trigger) or Chrono Cross. Chrono Trigger is a legendary RPG and no one should ever miss out on it. Chrono Cross is one of my favorite games of all time, and I would highly recommend it as well.

If you're looking for something really weird and pretty long, go for Legend of Mana. It's more of an adventure/RPG though. It's not at all what you might be expecting, but if you have an open mind, it's a fantastic game.

I haven't played much of Xenogears, but I like it so far. It's a Squaresoft RPG with giant robots.

Those are my recommendations.