There are quite a few very good titles on the DS actually, however I'll focus on Square seeing how this is a Final Fantasy website.

Square has been releasing tons of games for the DS. Notably Final Fantasy 3 & 4 remakes, The World Ends With You, a Chrono Trigger Remake as well, Not to mention Kingdom Hearts 358/2 days is coming out soon also. Those should keep you busy for a while, and if not, you could always check out Square's website for a complete list of there DS games.