F1, JGTC, BTCC, LeMans, WRC, Speed GT all fantastic racing.
If you ever want to see great young talent pushing themselves to 110% to prove themselves and make it into big-time racing, watch a Porsche Supercup race sometime. Spec cars, so all that matters is the skill and will of the driver.
For pure velocity and max driver skill, I love watching F1. Although I don't know what I am going to do with my Jaguar Racing stuff now...