Gameplay in JRPGs is tricky, because some games really don't hold up well in combat but still have good gameplay. For example, the dungeons in Dragon Quest V are pretty fun because of all the puzzles and secrets, despite the fact that the combat system is pretty much fight-fight-heal with turns. (In games like that it's more about how every battle wears you down as you go through the dungeon, than it is about how you win each individual battle - which is why games like that can't have loading times going into combat -- the fights have to be short.)
For combat systems, it's got to be the Grandia Series or Chrono Trigger. The Grandia battle system is actually very similar to Baldur's Gate 1 and 2, but without the pencil-and-paper rules in the background causing some weird problems, and with console-style controls.
A lot of people probably haven't played Grandia III. It was a mediocre game, and not nearly as good as the earlier Grandia games. But the battle system was incredible. I've never seen a battle system in any RPG that rewards player skill more, and very few manage to look as awesome when you're juggling enemies up into the air with team combos.
Chrono Trigger is just great because of the feeling it gives you. The tactics might not be bounds beyond everything else, but when Chrono leaps into the air and catches a fireball alley-oop on his sword before landing on the head of a giant snake, and you realize that you've just made a play right out of the concept art in the instruction manual, there isn't really anything left to argue about...
