Also NASCAR isn't number 1 by most metrics. Revenue, attendance, TV audience. It's second or worst by any meaningful measurement. That line is bandied about frequently but has no real truth to it.
I dunno about that. The biggest baseball stadium in the US has about the same seating as the smallest NASCAR track. The biggest nascar track has five times as much seating. (250K @ Indy vs. 50K at Coor's field) It has to be #1 for attendance and at least number 2 for TV audience.
I do know about that. Baseball has 30 teams that play 162 games per year each. It's far and away the most attended. I seem to remember them selling about 80 million tickets a year. I believe NASCAR is around 5 mil total.
NASCAR probably does have the highest average viewers at live events (they do have crazy amounts of seating) but they can't compete with baseball's 2400+ games per year. NASCAR has just over 110 events per year if you count Sprint, Nationwide, and Craftsman truck series. (I could be wrong on this, but I'm close. Pretty sure it's one race per series per week for 9 months.)
So NASCAR isn't #1 by any metric any person would normally use to define it. In fact, the Yankees alone sell almost as many tickets as all of NASCAR put together. The NFL, NBA, and MLB all outsell NASCAR by over 5x in terms of tickets.
NFL and MLB are also dwarf NASCAR in terms of revenue. Both are near $6b, which is roughly 3x NASCAR. (This also means that the NFL's average revenue per game is about 10x MLB).
Don't mean to nitpick, but he's currently #3, actually (http://en.wikipedia.org/wiki/List_of_billionaires).