Sounds dumb
Me and my mates get together once a year to watch the Dota 2 International event. Teams from all over the world participate for a prize pool of over 10 million dollars. It's watched by millions worldwide, with big live crowds, and every match streamed live.
It may sound like a cop out, only a game etc., but we've all been playing the game socially for years, and their skill level is orders of magnitude greater than ours, it's fun to watch.
We stream it on a big projector, have a few drinks and eat lots of take-away. It's just a sport like any other!
One cool thing about watching live is that you can watch it through the game client, you control your own camera angles, can check what stats you want, follow certain players etc. From a viewing perspective, it is leaps and bounds ahead of anything offered by real sports, and is all essentially free to watch.