#5 Chrono Trigger
Chrono Trigger is one of the greatest RPG titles of all-time and I had a blast replaying it on the DS. While it seems like a fairly standard JRPG on the surface, but it has revolutionary gameplay decisions that keep things interesting. Quite a few games lose their spark with time, but Chrono Trigger is as fun and interesting as it was the day it was released on the SNES.
#4 Mario & Luigi: Bowser's Inside Story
Mario & Luigi: Bowser's Inside Story is definitely the best Mario game you'll find on the system. The game basically takes the Super Mario RPG theme to the next level. The adventure has a great length to it, the characters are charming as you'd expect from a Mario game, and this is a game that any Mario fan should definitely have in their library.
#3 Dragon Quest IX: Sentinels of the Starry Skies
Dragon's Quest games are "hit or miss" is my opinion. This game was definitely a huge hit. If you're looking for something that's modern, yet has old school gameplay, this is the game for you. In addition to a great single-player adventure, Dragon Quest IX has a surprisingly good multiplayer mode as well. The game was a little easier than I had wanted, but there's enough content with this game to keep you interested for a long time.
#2 Bleach: The Blade of Fate
Bleach: The Blade of Fate was simply an awesome game and was very under-rated by game review community. I wouldn't rate the game a "10", but I'd certainly give it a very close score. It's the absolute best fighting game on the DS and a "must have" for fans of the series.
#1 The World Ends With You
I can't say enough good things about The World Ends With You. It's a masterpiece from an artistic standpoint and a masterpiece of a game. The gameplay is fast, the story is compelling, and the game is basically the best RPG you'll probably ever find on the DS. This innovative title is something you don't want to miss if you enjoy RPGs in the least bit.