A TotalConversion for EA's F1 2002 called GT Racing 2002. The most challenging & realistic PC racing game I've ever played and I've played a lot.
NFS is too easy... whupped it's @$$. Rallisport was a ton of fun... better than NFS

orsche and NFS:HP2 as well. NFS is very arcade... I'm pretty hardcore so I had my fun with it but it didn't feel REAL to me... like the you were driving the car on the bleeding edge on the verge of spinning out of control. GT Racing feels exactly like that. F1 2002 itself was too much for me... it felt more like being behind the wheel of a rocket ship rather than a real car.
I still haven't had time to try TOCA Race Car Driver and I haven't tried Colin McRae Rally 3 yet. CMR2.0 was an awesome rally game though. I even tried out EA's V8 Challenge. Decent game, very challenging as well but I liked GT Racing's dynamics better.