Actually, I'm gonna pick a weird one but: either Wild ARMs 3 or Wild ARMs 5.

I like Final Fantasy VII - IX slightly better than the two WA games, but I remember pumping 80+ hours into WA3 and 60+ into WA5 - and that was without doing any of the additional content. Both of them had heaps of optional dungeons, final bosses, challenging stuff that had to be done which I never got around to. I know the FF games have these as well, but I swear there's more in Wild ARMs, which would keep me occupied for a long time.

Also, Disgaea. Probably Disgaea 4. I could live in the item world for a very long time.

Are MMORPGs excluded ? If yes , then FF IX. If not , WoW.

Guild Wars 2

Either Xenoblade, a Pokemon game or Diablo.

Diablo? o.O

Geez. Google things you don't know or understand. xD

does Zelda count as a rpg?
if not Pokemon

World of Warcrack

Star Ocean: Till The End of Time.