I think this is it, for any sport really - but racing definitely.
To be honest, I find Nascar more interesting as a sport than F1. Yes, the glamour, the speed, the unlimited engineering, the international element . . . all of that is really cool and F1 is the premier auto racing series in the world without peer. I'm fully on-board with that and really like F1.
But when it comes to watching the actual sport, the event itself, Nascar is more interesting to me. In any given Nascar race, there are about 15 to 20 cars (out of 36 to 40 depending on the race) that are capable of winning the race. The races are long (2.5 hours to 3.5 hours) and so the story line is always developing - there are many variables always in play. And the teams are able to adjust their cars for better speed or better grip or whatever through the race far more than an F1 team can. So there's much greater movement through the top 5 and top 10 through the race. And there's so much passing - the average Nascar race will have more lead changes than five to ten F1 races, and some Nascar races might have more lead changes than an entire F1 season.
Ovals may seem boring at first but when you get the hang of how a car gets around an oval with speed and you can see it with your eyes, and then when you watch how they have get around the oval at absolute maximum (on the edge of losing it) speed with many other cars often inches away doing the same thing, it becomes very exciting.
Personally, I find Nascar to be the most intellectually stimulating sport that I have watched, it explains why I have watched (or listened to in the car) probably 90% of all Cup series races since 1996. There's so much going on, so many variables, so many things to keep track of in your mind as you're watching . . . not saying you do these things deliberately with effort, but in years of watching you just keep track of it so when some car that was running 10th makes an adjustment in the pits and starts moving up, you notice that and it's cool. And you can notice multiples of those kinds of developments as they happen through the race. People would probably be surprised or dismissive to hear someone say that they think Nascar is intellectually stimulating but I completely find that to be true. If you know what you're looking at.