Hmm, I don't play many multiplayer games.. I would've recommended Heavenly Sword and Uncharted as they are both tops, but both are single player. However, both are also visually engaging enough that my friends never seemed to mind sitting back and watching me play... maybe they were just polite.
Kain (cain?) and Lynch has co-op, which is good times, but I found that it still wasn't that great of a game. I had a pretty good time playing through it with my gf, but we spent the entire time either frustrated at having to do certain sections over and over and over ad-nauseum or just laughing at how ridiculous the game was. I had fun, but I wouldn't call it a good game. It also has online multiplayer that I never even bothered with.
Tekken 6 will be out later this year.. I'm really looking forward to that. there is a 1080p remake/update of Tekken5 with online play that's probably pretty good if thats your thing.. we got the offline version because we weren't really interested in getting beat by people who were better than us.
edit: Why get a ps3 to play ps2 games? We're on to bigger and better things son!