Get one of the Monster Hunter games, I'm not entirely sure if they have any for PS3, though they had them for PS2. Ridiculous replay value in them, pick one up.
Last year I had a student that was nuts about Monster Hunter. The games do look pretty neat. I think there is one coming out for the Wii later this year and a 360 one coming a bit later. From what I understand the PS3 version got canceled. I think I'll look into the Wii version once it's been out awhile.
Demons Souls is good
I played border lands online and I really couldn't find anyone to play with around my level everyone was much higher and no one used a microphone (But then again that's basically all of the PS3 community).
Tbh I don't know of a game that I would spend 60 dollars on as of right now. the bad company 2 demo is fun
Go rent dante's inferno for a week
And for killzone 2 it was fun but for some reasons that are probably fixed by now 1. the controls were kinda hard to use but it's something you get used to and 2. there was horrible lag with kills, you and someone would be shooting eachother and then you would both die or you'd shoot someone and they run behind a wall and die. hopefully that is fixed but I haven't played that game for a LONG time