From the topic title I guess you enjoy SRPG's and the best ones for the DS have already been mentioned.
Shin Megami Tensei has a great story, a different battle system, and is a great game.
The Luminous Arc series does not have great controls and the battle system is basically no different than FFT. The story is entertaining and the dialogue is funny.
Disgaea has good graphics, refined battle mechanics, lots of customization, and you can play it for scores of hours without getting bored.
Rondo of Swords, which is my favorite SRPG on the DS, has a completely revolutionary battle system, tons of customization options, a lengthy story, and plenty to do. It is kind of challenging though.
Valkyrie Profile: Covenant of the Plume is a very underrated SPRG that does a lot of things well but is not great in any one area. I would still recommend it for SRPG fans.