If you're into fighters, Marvel vs Capcom 2 comes out in about a week and there's already Super Turbo HD Remix, both running for $15. Most people really like Wipeout HD, so if you've ever played the series and enjoyed it it's probably a good pick up at $20. Fat Princess just came out and it's a pretty good "capture the flag" type game. I don't think it's really worth $15 for it's single player campaign so if you don't plan on playing online with it I wouldn't get it. There's also Flower, which a lot of people seem to like, it's just that I never bought it so I wouldn' know first hand how the game plays.
Wild Arms is a decent enough RPG series, though I'd recommend Suikoden over it if you have to choose. Suikoden is probably one of the best RPG series around, though the first one is rather short and you can beat it in about 15 or so hours. The second one is much better and probably one of the best RPGs ever made, but sadly it's not on PSN and the only way to get it is by paying $80+ on ebay.
