Lots. Sports should be the universal language, and it should appeal to everyone. From the highschool drama queen, to the basement nerd. From the I-inherited-my-dad's-estate millionaire, to the hobos on the street. From that one guy, to that other guy. And maybe that one guy, too.
As is, sports really only appeal to one demographic. The sports-loving type. That's horrible advertising. Do you see any company sticking to the sports-loving type demographic for their product? Does any politician only lobby sports-lovers as he tries to get into office? Hell no! So neither should the world of sports. They should - no, must - expand into all regions of life, into all demographics. Don't settle for the demographic others won't!
There are a bunch of things the world of sports could do to attract more people. In fact, some are so obvious, it's amazing these haven't been implemented already.
Lethality is the first. You want to get better performance out of your athletes? You want to get the crowd into a bloodthirsty rage? Kill some players, or put the threat out there. Give the ref the power to kill players whenever he deems fit. Give all the players guarding bases chainsaws. Randomly spray the soccer field with napalm. Put landmines on the football field. This does two things. First, it puts Darwin's theory to work. The bad players get weeded out, so only the good remain. The good players
Put sparkly vampires in the game. Then behead them part way through.
This gets you the whole Twilight fanbase and the disgruntled significant others of the Twilight fanbase in one fell swoop. Also, you kill a sparkly vampire. What's not to love?
Throw in an angsty teenage wizard, and you get even more people!
Make a leveling system for fans. Give them experience for every game they watch and every piece memorabilia they buy. The higher the level, the more insider content you get, like the post-game commentaries nobody really watches. Then people will also watch the commentaries just because they're high enough level to. By doing this, you get every power-leveler lifeless nerd into your fanbase. Also, someone will set up a sweatshop to level grind sports, so that's a chunk of Asia right there.
Pay fans to watch. After all, more people watching means more revenue. And more people watching. Why doesn't this already happen? I know I'd watch a football game for minimum wage, and I wouldn't even cry foul for child labor!
My final suggestion is that, at random intervals, you have midgets run onto the field and headbutt a random player's crotch. Okay, this wouldn't really increase viewership (Well....maybe...) but it would be freaking hilarious to watch.