I know a friend who really liked the "Fight" game.
From what I heard "Kung Fu Rider" is suppose to be pretty fun. It's a wacky Japanese arcadestyle game.
I second the motions of HOTD but I didn't think HOTD 2 and 3 were on PSN, just Overkill and 4. Huh.
"The Shoot" is suppose to be pretty fun if you want a shooting gallery thing.
I plan to get "Sorcery" and I'll tell you what it's like.
Even though no one mentioned it here the original "Sports Champions" is pretty fun. I haven't played the second.