There are plently of good RPGs for GB/GBC.
Dragon Warrior 1 & 2 Remakes
Dragon Warrior 3 Remake (I like it better then the NES version)
Lufia: The Legend Returns (a personal favorite)
Final Fantasy Adventure (Seiken Densetsu)
Final Fantasy Legend 1 (Saga 1)
Final Fantasy Legend 2 (Saga 2)
Final Fantasy Legend 3 (Saga 3)
Pokemon Series (it isn't that bad)
Dragon Warrior Monster Series (like Pokemon, but with more breeding)
Azure Dreams (Rogue clone)
Harvest Moon Series (Sim/RPG)
Star Ocean: Blue Sphere (only partial Translation patch available though)
Crystalis GBC (I actually like the original NES version better)