Have you any interest in the Pokemon games at all? Pokemon Black and White are coming out in the soon time (I'm not exactly sure how soon) and Pokemon Pearl, Sapphire, and Platinum are already out, as well as remakes HeartGold and SoulSilver. I have also heard good things about Final Fantasy XII: Revenant Wings, and the Final Fantasy Tactics: Advance series is pretty good, though those aren't strictly RPG's. Of course, if you've never played them before, Final Fantasy III and IV are great games.

Unfortunately, I haven't played a lot of RPG's for the DS myself. I will say that I would not recommend Sonic Chronicles; the battle system for that game is really frustrating and slows the game down badly, and the soundtrack is made of poorly done midi files. Kinda sucks, because the story and characterization was pretty good. Anyhoo...

Wuv, Yer Mom