DS also has some good RPG's.

There's Final Fantasy 1, 2, 3, 4, 5 and soon 6. Which I think is absolutely great to have portable! Then there's the Mario and Luigi RPG's (to be honest, I think they should remake Super Mario RPG for DS), Golden Sun series, Mana series, and more that I can't think of right now.

Then you have some other cool games like Mario Kart, New Super Mario Brothers, Elite Beat Agent, Advance Wars, Yoshi's Island, and a whole range of GBA games.

The PSP looks interesting for me though, for FFVII and Valkyrie Profile, but nothing more.