If you're a racing sim junkie, then you need to have one of Logitech's driving wheels. There's no way around it. The controller is no match for the fun and pleasure you will derive from having a Logitech wheel. The Driving Force Pro is compatiable with not only the PS2, but the computer as well, which opens up the amount of racing sims you can play.
The wheel and pedals themselves are of great quality. The wheel feels great to hold, and the force feedback gives it a lifelike heft and transmission of vibrations from the road. There is a sequential "stick" shifter on the right if you really feel like going 100% sim, but there are paddle shifters on the back of the wheel as well. An entire PS2 button setup is on the wheel itself, so no need to have an extra controller sitting around.
If you find yourself playing racing sims often, do yourself a favor, and get a Logitech Driving Force Pro.