I haven't read all the thread yet, so if someone pointed this angle out already, apologies. I'm not a big sports fan (enjoy a good fight though), but I have been to some events (football games in HS due to being in the marching band, college football due to my buddy going to Penn State, and pro baseball games due to my brother and friend being fans). Going to a game can be exciting and I can see being caught up with the dynamic of the crowd. I certainly don't follow any typical pro sports, turned down several offers to play Fantasy Football, and typically change the channel if a game's on.
But, I also would rather watch a well-crafted story than reality tv everytime (I do like an engrossing documentary here and there), and I struggle to find interest in politics (I've been educating myself more and more the past 2 elections). Most of my interests (that don't involve friends or family) and escapist entertainment, whether reading, watching, or playing, are centered around fictional characters in fictional stories.
I may not be a "sports fan", but, I do love a good sports movie. Inspirational, comedy, etc. The Rocky films are some of my faves (my father and I would bond watching them as I was growing up). I think that some of the appeal to the sports fan is, amidst the plays/statistics/maneuvers/positions in a real world game, there are real stories taking place down on the field, real human conflict, struggle, drama. I just prefer the sports film medium because it edits out most of the boring parts, often inspires or makes me laugh, gets me right in the middle of the action, requires less time investment, and occasionally shows me boobies.
EDIT: Despite what anyone might think of Jimmy Fallon or romantic comedies (or the Sox), FEVER PITCH does a good job of showing why sports fans do what they do. I could easily relate to the healthy and, unfortunately, unhealthy fan behavior.