Obviously there won't be a Gran Turismo for the PC. But I suppose it depends on what type of racing game you like.
If you like the Arcade type games then Need for Speed are always pretty good however my personal fave is Test Drive Unlimited especially when you unlock hardcore mode the handling becomes more realistic.
If you like sims I still think GTR2 is the best especially with TrackIR installed. By the way TrackIR is supported in Test Drive Unlimited as well.
Damn it, I wish it should have look good on PC. Acutally really it for my little brother crazy love over any car racing game either on street or World Rally Car but not racing track like F1. Also he got his favourite on Grand Auto Theft game and Black Monday. That why he ask me question about GT.
Race: The WTCC game
Need for Speed
Colin McCrae Dirt.
Check out some reviews to decide which best suits your brother's personal tastes. And use a gamepad (I like the Microsoft 360 controller) or a wheel (I've got Logitech Force Feedback one that only cost £40 but is excellent). Racing with a keyboard is naff and frustrating.