dont diss chinatown wars. almost every review has said the gameplay is better than the psp ones. if you have have played gta 3, vice city or san andreas, then youre just replaying it on a psp since its a port of the game. chinatown wars has so many innovations and new ideas that are great, and the graphics really arent even that bad... pictures are deceiving.
id go with the ds lite man. i had pokemon diamond since july 2007 and i still find myself plying it a lot, and now that platinum is out, you can play even more on that. theres also a new zelda coming out in september (or october), so you really cant go wrong with a ds. if you do get one, you should really look into a flash card. i have one, and it enables you to download full ds games, and homebrew, and you play them on your ds for free. pm if you have any questions about it.