OOORRRR, Instead of asking us of our opinions, you might want to check out Game Rankings Top 10 or Top 20 games on the PSP.
With that said, on the PSP there are really two types: The games that are quick fixes,( really easy to play or don't take up hours of your time) or the ones that are more like the standard releases for the PS2. ( longer games)
My Personal Top 3 of each type:
A. Quick Fixes= 1. Patapon, 2. EchoChrome, 3. Loco Roco
B. Standard Games= 1. God of War: C.O.O. , 2. Final Fantasy Tatics ( don't worry about the story on this one, it's an update of a previous version) 3. Metal Gear Solid: Portable Ops
Check us out at the Vindication Gamer Network on Youtube.