It'll be an odd one compared to everyone else, but DiRT 3 with some good music playing in the background is awesome.

The physics are awesome, a bit arcady but reasonably realistic and manageable even on keyboard and the replay mode is amazing, makes even the shittiest driver look pro with its camera work.

And the rallycross modes and the montecarlo track are amazing.

With rally cross being high speed dirt circuit racing. Constant bumping and AI cars losing control and messing up if you pressurise then enough makes it a fun experience. Dirt 2 is indeed better in all areas like voice lines in rallycross ,except for the handling and rally but I started with dirt 3 so that's what I am sticking with