Personally, any professional level motorsport that doesn't advance the technology of the automobile is pointless and wasteful. It is a waste of perfectly good gas, waste of engineering efforts, and a waste of time. NASCAR is a perfect example of this. The only way this sport would be entertaining to me, as it is now, is if the races where half as long, and betting was involved much like horse racing. Otherwise making 2000 left turns at 150-200mph is boring, pointless (aside from being a marketing wet dream), and wasteful.
Series like F1, WRC, ALMS, and Touring Car Championships are all contributing to the advancement to automotive technology. The races are shorter (except ALMS which are long to test for the long-term durability of new technology), the drivers are subject to higher G-forces, more treacherous conditions, include racers from all over the world, all the while attaining the same 150-200mph (or more). It is for this reason the races are more entertaining to watch.
Now I have nothing against ovals. I watch IRL as well, and they are, like NASCAR, driving on only ovals with the exception of 2 or 3 races. But since these cars are advancing the world of automotive technology, and have an international field, I can bare to sit through a race. Ovals are also great because it's the only form of motorsport where you can see the entire race right before your eyes and not miss a thing.