The DS is pretty shitty when it comes to RPGs. I can't vouch for the PSP either because it's mostly just a dumping ground for jRPGs but a revised edition of Star Ocean 2 (you know, the only GOOD one) comes out early next year HOW YOU CAN SAY I LIKE RPGS and pass that up is beyond me.
This. They generally fall into 3 categories.
1. Final Fantasy (or Final Fantasy clone)
2. A crappy stratergy RPG that is clearly an inferior copy of Final Fantasy Tactics.
3 Or "INNOVASHUN CONTROLAN" which means you have to use the touch screen and it is done is a stupidly fucking awkward way that ruins the whole feel of the game. Actually, most DS RPGs fall into this category. You can literally play 90% of the game with the control pad/buttons, but there is always some little fucking gimmicky gameplay element that you HAVE to do and you HAVE to use the touch screen for, "touch the screen to unleash your special attack!!", or "you have to draw this with your touch screen" or the most annoying "you can use the control pad/buttons for everything in the game, except for in a fight. Enjoy having to adjust to two totally different control schemes!".
In general, DS RPGs are not that good... Then again, the PSP has just as poor a selection of RPGs, but at least it has like... 2 decent ones (even if they are remakes of PSX games).
My advice is just get a DS emulator for your PC. They are easy to find, and work pretty well with good support for most games. What is the point in wasting money on a DS AND a flashcard when you could achieve the same results for free?