That really was not needed. You just want to start a flame war, don't you?
...........................................
Anways, I have heard that NFSU:Rivals, Lumines, and Untold Legends are pretty good. I have yet to play them (because I do not have a PSP), but from views from magizines, online, forums, etc., those have been mentioned.
Super Mario World 64 DS, or course---er, wait...PSP? Dang.
Seriously though, according to Judgement Day, a game review show on G4, the best racing game is Urban GT Turbo or something...so grab that if you like racing junk.
Ridge Racers, Lumines, Twisted Metal: Head On are among the best you can get along with Wipeout Pure too. Even though its expensive people still want a PSP, everyone I know has one. Some even traded their previously owned DS in for credit towards a PSP. HA!