I'd say the best car is the Zonda C12 S 7.3,if you put on all max parts (except racing exhaust and turbo) and the put the auto gear ratio up to 25,it will do 0-60 in about 2 seconds and can reach and hold 257 mp/h!
My fav is the Ford GT LM Race Car Spec II,it had amazing handling,better then the F1 car,and could reach 220 mp/h.I also like the Mercedes-Benz 190EL Evo II and the touring car version,It was fun and had good looks and speed,handling was great too.
Sadly I am grounded off PS2 until further notice,but today I snuck on.