i have a huge respect for oval racing, even for NASCAR drivers, it may be boring to watch on tv, but yeah in real life its pretty damn intense. it being an oval with 4 turns does make it much much easier to learn the track, but all that means is people can push harder and harder and do the corners extremely well. plus there is so much strategy with drafting and everything.
BUT, i still respect road racing more, its just takes more overall driver skill, there is much much more hard braking, downshifting, passing under braking, so many more lines, and still plenty of drafting.
the indy 500 is up there, but definatly not the greatest spectacle in racing.
anybody who sees a big race for their first time is going to think its the best thing in the world, all that power and speed and intensity blows your mind, go to a local track and watch a little scca or nasa event, and you will have an extremely fun time.
IMO the 24 hours of nurburgring is the "greatest". a 20 corner race track is usually pretty high up there in size, most tracks vary by about 10 or so, the difference in size between a 10 corner track and a 20 corner track is pretty huge, its takes much longer to learn the 20 corners and 10 corners isnt exactly small to begin with. the nurburgring has 73. it takes a good racing driver 50 or 60 laps to learn the corners. twice that to lean the line, and hundreds of laps to be any good at it, and you will still be making mistake after mistake each lap. in a good day of practice you might get 10 laps or less in. plus there is an insane amount of elevation change in every part of the track, you dont realize it in video's or video games, but some of those hills are crazy steep. elevation change can make what would be the easiest corners, extremely hard, IMO its the most challenging part to any race track.
i talked to a guy who races the 24 hours or nurburgring, he's done 10 or so races there, and over 100 endurance races. and he told me all about it, he said one of the scariest parts is racing at night when people have campfires, first of all its night and your constantly doing well over 100, but you will be coming around already blind corers into slower traffic, go through campfire smoke making most of the corner completely blind, you have to trust that you remember every little detail of that 1 out of 73 corner right when you come into it at 140+. it takes an insane amount of skill, smoothness, and consistancy to do even an easy 12 hour endurance, a 24 hour race on the ring is just crazy. he had a good friend die just because he got his corners mixed up, he went into a corner about twice as fast as he should have, and there being no runoff, smacked into the wall at 140. about 80 drivers and bikers die there per YEAR!