Are most of the PSP games ports from PS2?
No. There are some games that people could see as “ports” (GT4, Tony Hawks Underground 2 and Hot Shots Golf for example), but the amount of games like that are very few compared to all the brand new games being developed for the PSP. Those “ports” all feature new content aswell. GT4 features wireless play (aswell as online), THUG2 features 4 new levels and more players to choose from aswell as wireless multiplayer, Hot Shots Gold features 4 new maps, 10 new playable characters and wireless multiplayer. Need For Speed Underground Rivals features brand new levels and wireless multiplayer specifically made for the PSP. Every game features new gamemodes aswell. Sony have actually said that they don’t allow games to be ported without new content/features. Source: IGN.