I haved enjoyed (at least a little bit) every PSP game I own. I really reccomend trying LocoRoco, Crisis Core, Crush, Disgaea, Star Ocean, and DJ Max Fever in addition to your list. All are completely awesome.
And I absolutely love DJ Max. It's pushing to be my favourite PSP game.
"We'll toss the dice however they fall, And snuggle the girls be they short or tall, Then follow young Mat whenever he calls, To dance with Jak o' the Shadows."