If you mean action-RPG then yes, there are several, the most prominent of which is Zenonia. I'm not entirely sure what you're asking though.
No, nothing of Kingdom Hearts quality. There are 3D action RPGs like Ravensword, Dungeon Hunter, Crusade of Destiny, etc, but imho nowhere as great as Kingdom Hearts. Most RPGs on AppStore so far have pretty generic storyline and characters, nothing too good.
Crusade of Destiny is NOWHERE close to Kh. Not even to be mentioned in the breath. I guess we'll hve to for Kingdom Hearts: Coded
If you'd be satisfied with a solid 2D action RPG check out Zenonia or Hybrid. There are lite versions available for both.
Aralon [http://forums.toucharcade.com/showthread.php?t=47272&page=5] or Ravensword 2 [http://forums.toucharcade.com/showthread.php?threadid=47996], both upcoming, might be similar enough for your tastes.