Cannot recommend Panzer Dragoon Saga enough. One of the best looking Sega Saturn games. Its a JRPG with turn-based battles, a super unique system. Along with the rest of the Panzer Dragoon series (though they are on-rails arcade shooters), not sure the RP3 is powerful enough for original Xbox games.
For driving, I am sure you've already been recommended the usual, but to reiterate: anything from Gran Turismo, Star Wars Episode 1 Racer, Collin McRae, WipeOut, Need for Speed, and Sega GT are all good picks.