World of Outlaws 2002 is my favorite PS2 game there is. I have rFactor and the Bandit sprints from 321, but it isn't so easy to pick up and run with. Another dirt mod that has been occupying some of my time as of late is dirtfactor which is latemodels, but fun nonetheless. I haven't played Road to Knoxville, though I have heard some unhappy reviews?

Amazon.com has a few copies of WoO 2002 left so check it out there.