I root for the Chicago Cubs, but that's just because they have a long proud tradition of failure. I feel like cheering for a team with such an incredibly long losing streak builds character, and if they ever do win, it will be rad to have been supporting them the whole time. Its also definitely has a certain amount of local pride involved, as well as just kinda being raised to think that if the cubs ever win the world series, all wars in the world will end and peace and unity will reign supreme forever.
I was down for the bulls with MJ, but again, I'm pretty sure that after growing up where I did, if you didn't worship the ground Michael Jordan walked on, you would face consequences.
Right now though, I've been working the summer at the Giants stadium, and NOTHING is better than watching those fucking arrogant asshole fans get dissapointed when their team gets its ass kicked.
But I think in the end, if you like a sport, if you don't pick somebody to follow and get behind, its hard to stay interested.