Well if you ever plan to get an NGP you should get your titles on PSN, though you'll pay more than the games are worth and have to buy memory cards, and not have the best game on the system since it's not on PSN.
If not the first game you should get is Kingdom Hearts, after that games like MGS Peace Walker, Portable Ops, the entire Monster Hunter series, Little Big Planet, Resistance, Crisis Core, Tactics Ogre, and some of the PS1 games that were ported to the PSP like Ape Escape and Final Fantasy Tactics.
There's a number of other titles I could suggest but those are the best titles that will likely also last the longest.
MaxwellGT2000 - "Does the amount of times you beat it count towards how hardcore you are?"
Wii Friend Code - 5882 9717 7391 0918 (PM me if you add me), PSN - MaxwellGT2000, XBL - BlkKniteCecil, MaxwellGT2000
