Sports essentially boils down to male appropriate drama.
Sports aren’t fake (other than wrassling) but it is manufactured. However, that doesn’t mean real drama can exist between rivals.
You might want to mention that to my wife sometime when figure skating is on.
…and you might want to put on some protective headgear first. 
I was trying to just differentiate sports drama from the Meredith Baxter kind.
I’m sure there are dudes out there watching Oxygen.
Actually, yes, there are (the name of one of my kayaks is Oxygen, and there are some youtube videos of it out there on teh intrawebs).
Um, hello, there are female sports fans here too, you know! We don’t just watch because the “oh my god, that guy is sooooo freaking hot!!!”
For me, the fun of a baseball fan is twofold (and in opposite directions). I work professionally as a scientist, so the number-crunching stathead stuff appeals to me for much the same reason as my actual lab project does - it’s an interesting and very complex system, but one that can be approached objectively if you break it down into the right numerical components. The advances in baseball analytics over the past few decades, and especially within the past five years, is fascinating to me.
On the other hand, I’m also an avid reader, moviegoer, and TV watcher. I love stories. And the stories of sports offer one thing that the former simply cannot: they are unspoilerable. Seems obvious, maybe, but there’s something about going into a game or season with absolute knowledge that you cannot predict the outcome. Sure, you can project what may happen based on the relative talents on each team, and home field advantage, and all that. But you never know. You can’t know. You’ll always be surprised, at some level.
A side effect of “unspoilerability” that I also enjoy is that sports stories don’t have to follow narrative tradition, making them truly unpredictable. As much as I love a good book or following the narrative arc of a well-written TV season, those ultimately come with certain expectations - an introduction, rise in action, climax, denouement. None of that is certain in sports. A promising season can sputter to a disappointing halt. A team that nobody expected to make the playoffs can squeak in by one game and then go on to win the whole thing.
Here’s an example just from the first month of the 2011 baseball season: the Red Sox came into this season as near-unanimous favorites to win the World Series, but then started the season 0-7 and currently sit below .500. Who would’ve predicted that? And now the narrative for Red Sox fans, which coming into the season seemed to be one of dominating conquerors rolling over their enemies, has morphed into a fight for survival and a nail-biting struggle to turn things around.
Well, this weekend I was at two different baseball games that each provided a different example of why I enjoy sports:
The first involved a perfect game going into the 8th inning. My team was already up big, so the outcome of the game was not in doubt. But the possibility of seeing something in person I’ve never seen before had me as nervous at a game as I’ve been in years. It was entirely unscripted drama - something I had no control over but was a on edge about as I’ve ever been in a movie or play.
The second was just sitting under a bright clear sky watching a well-structured game that I knew inside and out without having to worry much about the world or my life or anything other than 18 great atheletes playing a kids game. There is something liberating about that, if only for a few hours.
The final reason (which didn’t really come into play for me this weekend) is the the sense of community it can provide. In St. Louis I can talk to almost any man or boy about the Cardinals and immediately connect with them on some level. Perhaps it is a banal connection, but it is something. It also ties generations together - I can spend hours talking to my grandfather about the great players and games he saw and understand it perfectly, much more than I can other stories from his era.
I’m not a sports fan at all, but I don’t think its appeal is mysterious. One thing I’ve seen mentioned only obliquely that I wonder about: isn’t the vicarious risk a huge part of the thrill? I mean, here you’re watching people putting themselves in a competition where someone is going to lose in front of (sometimes) tens of millions of people: while the consequences of the loss are manufactured, those consequences do exist. And nobody knows in advance who will face the risk and succeed, and who will face it and fail. That’s pretty damned exciting, and it can give an adrenaline rush to the folks watching.
As Mike Greenberg says, sports is the ultimate reality TV. Part of what makes an athletic competition geat is that the outcome is unscripted. This is especially exciting when you have a rooting interest in the competition.
Another appealing aspect to sports for me is strategy. Baseball and football employ heavy use of strategy and those are my favorite sports to watch on TV (or in person) because of that. Basketball employs strategy too, but the appeal factor of it (for me, anyway) is the sheer excitement of nonstop action. NBA games feature a lot of crowd-energizing propaganda.
Finally, as others have mentioned, watching pro sports is watching excellence. Most pro athletes have mastered skills in a way that your average joe could never achieve.
So you admit, then, that that’s at least one of the reasons?
Well I wouldn’t kick Sidney Crosby out of bed, if that’s what you’re asking.
But that’s not why I watch sports.
That’s good, because poor Sid’s been injured enough lately.
Watching a game where I don’t have a rooting interest can be enjoyable, but it’s a distinctly different experience for me from one where a team to which I’ve developed an emotional attachment is playing.
By essentially fooling ourselves into thinking that something trivial is of vital importance we trick our brains into releasing endorphins, serotonin and dopamine. It’s the equivalent of shooting up heroin but it’s cheaper and relatively non-addictive.
I’m a fan of many sports and I’m convinced the moment I was physically happiest in my entire life was when my college hockey team tied a championship game against its bitter rival with 33 seconds left. I can watch a clip of that goal 8 years later and still get a physical rush.
I think that Vision Quest’s explanation works for me.