Now that I've played Burnout Paradise, as much as I love it, I don't think it's as good of a candidate for a "hot-seat" (group of players handing a single controller around) crash competition as a previous version that I've played. The game is very open, and there's lots of driving around looking races to run, for things to smash into, or other "drivers" (this seems to be the term that they use only for your competition, not for the other casual drivers on the road) that you can try to "takedown" and get their car.
That being said, I hope to have MotorStorm: Pacific Rift soon. My brother has it but said he never plays it because he's addicted to GTA. It's got a two-player split-screen mode, so that would be cool for party time.
The only multi-player games I have at this point are PS1 games, which are cool, but definitely won't show off the power of the PS3. What PS3 games do you guys have?