I myself have an NDS but the games are pretty unsatisfactory, the graphics look like toddler scribblings and story lines are boring. The problem with PSP is that most game creators have given up on it, don't know why but that seems to be the case.
Thanks but i am in the NDS gaming motherland (japan). There are so many games here (although in japanese) with nice gameplay. The graphics is not a big problem since the screen is small i guess.
Probably not all games released in Japan are released where I live. And it could be that you like a whole different sort of games, but for me the NDS is a flop.