Cool to see all the votes for NFS: PU, its also one of my all time favorites
The whole starting in the 50s and going up from there was so well done, it had pretty much everything I want in a racing game other than brand variety
(but Porsche is great so whatever)
Of course, its impossible not to mention Gran Turismo... Im still waiting for the day something like that will be released for the PC, it was just so massive in every way, pretty much the ultimate racing game
And another personal favorite is CMR 4 (although 2.0 is generally considered the best), its the only racing game Ive ever played "seriously", as in constantly trying to perfect every course, because they were all so much fun... Nowadays I just go through the career mode once and get too bored to do it again