There was a thread here that I had saved a few months ago where people had recommended lots of cool lesser-known DS games. I finally got a flash cart a legal means of obtaining games but sadly all of the comments on that post have been hidden by the admins. Would be nice if we could start a new thread for recs
I really liked Castlevania: order of ecclesia which I played a couple months ago, the DS version of ff4 has been pretty fun so far too.
Never got around to finishing that one, but I remember buying it at launch. It's pretty tough. Dawn of Sorrow and Portrait of Ruin are also great picks in the franchise. Hard to miss with the DS and GBA Castlevanias!