MotoGP and the American Le Mans Series. ALMS probably has the best racing of any series in my opinion. In addition to having multiple classes on the track at the same time, the GT field is insanely competitive. This year its going to be made up of Corvette, Ferrari, Porsche, BMW, Ford, Jaguar, Aston Martin, Lamborghini, and maybe Panoz. The first four are always fighting it out for the class win, the Ford GT’s, while usually slow, look great, the Jaguar is entertaining in its own way (never making more than 2 or 3 laps), and Aston and Lamborghini are new elements this year.
The FIA GT1 World Championship is by far the most fascinating race series I have ever watched (apart from F1, of course), the cars are so closely matched and yet they are completely different. They have driven some of the most spectacular racing that I have ever seen, on some of the nicest tracks all over the world.
I myself fell in love with the Sumo Power Nissan GT-R, and I think it is the most beautiful car in the world.
GP2 and GP3 simply because they are feeder series to F1 and it’s good to keep updated! I like WRC, BTCC and the DTM series is good to watch too. By and large I’ll watch any motor racing, just can’t stand bike racing.
@ MattHT finally someone joins me. Bike racing is pointless. An infinite amount of overtaking makes it infinitely boring to watch. Plus the bikes are so small on big tracks such as Abu Dhabi. It would only be fun if they ran on 2 meter narrow roads so the had some possibility to block each other.