Don't know about PS controller, but it does support 360 controller.

Quite an understatement, playing it with 3 other people on nightmare is hilarious. I'm pretty sure the multiplayer ports like Skulltag and ZDaemon allow co-op with a lot more players than that. And when you're done with the main episodes, there are infinite amounts of user created maps and episodes.

System Shock 2 is a great co-op game too, though extremely buggy.