For me, for both football and baseball, the top of the list goes:
Cleveland
Pennsylvania
Pennsylvania
Wisconsin
Cincinnatti
Cleveland is where I’m from, and you just have to root for your home team. Even Atlanta fans are justified, if that’s where they’re from. So, Indians and Browns
My family’s from western PA, and I went to undergrad in Philadelphia. I figure both cities rank about equally, so I resolve the question by rooting for the Steelers over the Eagles, but the Phillies over the Pirates.
I like the Packers because I think the notion of a community-owned team is just so cool, and I’m grateful to the Brewers for all of those times back in the 80s when they provided an opponent the Indians could actually beat.
And I’ll root for Cincinnatti just because it’s still my home state, even if not city.
Lately, I’ve been rooting a lot for Seattle, too, because there are a fair number of folks from Seattle around here, so if I’m watching the game with them, I’ll root for their team to be polite.
Near the bottom of my list for both sports is Atlanta, because from what I’ve seen, Atlantans just can’t appreciate their sports teams. The last time Cleveland and Atlanta faced each other in the World Series, the Cleveland tickets sold out in February from people advance-ordering them just in case we made it. The Atlanta tickets were still being sold at the gate at the start of the game. There’s something wrong with any city that can’t sell out a World Series game.
For baseball, that’s the bottom of my list, but for football, the Broncos and the Ravens are even lower. The Broncos because there were just too many times when they kept the Browns from reaching the Super Bowl, and I don’t think any Clevelander needs explanation for the Ravens.
In between, I mostly go by geography. I’ll generally favor the Midwest over the Eastern Seaboard, the East over the South, and the rest of the South over anywhere in Texas. If it’s a couple of teams I don’t have strong feelings for, I’ll also be swayed by the alliegances of whomever I’m watching with.
Finally, I don’t really follow basketball at all, but I’ll root for any Villanova alumni I happen to notice, especially Kerry Kittles or Jason Lawson, and I’ll root against Tim Thomas and Allen Iverson.