IMO the best racing sims out there are the games produced by SIMBIN.
GTR
GT Legends
GTR2
Race
Another really great game is Richard Burns Rally, but I don't know if it's in circulation anymore. Another game which is most definately out of circulation but will run on most any computer (since it's 10 years old) is Grand Prix Legends. You can find copies here and there and it takes some modification to run properly on modern PCs but it's still quite good.
All of these games are much more SIM-like than game-like, in the same way Microsoft Flight Simulator is a sim compared to arcade shooter type flying games. I think you'll be very impressed since it seems the games you're familiar with aren't really true sims. It's a whole new world out there in driving sim land. Check out
www.racesimcentral.com.