Of the mega sporting events, Daytona 500 would be my pick. The NFL Super Bowl, MLB World Series, NBA Finals, PGA Masters, or U.S Open, included.
Unfortunately, it is the furthest possible distance from me in the U.S., almost 5K, from Hawaii. Would love to attend the Las Vegas race in Feburary or Fontana, Ca. event in October.
Lived in So Cali in the late Seventies thru mid Eighties. Attended four CART Long Beach Gran Prix, and two California 500's at the old Ontario Motor Speedway.
The best times of CART, with the Unser's, Andretti's, Foyt's, etc. All that's changed. No form of auto racing more competitive, or colorful, than NASCAR today, IMO.