Well, that is an interesting question. I guess that I've been a "fan" since 1965. That's the first game I remember being at, at age 7. "Dad, who are the guys in green?" Seriously ... we had a black and white TV. So, my first exposure to the game was geography, or perhaps birth-right, as someone else mentioned. As you're all aware the Packers were a festering cesspool through most of my youth - and they may have been a steaming hot pile of dog crap, but, they were OUR steaming hot pile of dog crap. Call it what you will but the Packers made Green Bay and Northeastern Wisconsin "big league" although ostensibly, nobody wanted to play here.
Now, in a parallel universe, would I be a Vikings, Bears or Lions fan if the Packers didn't exist? Maybe substitute Duluth for Green Bay in this universe - would I be a fan of the Duluth Eskimos? Probably not even though someone once said that "without the Packers, Green Bay is Fargo". Would I be a "fan-of-the-game" if Dad and Grandpa hadn't chosen to expose me to the game and the Pack? Who knows. Would I have sat through the 70's and 80's in Lambeau having my finger nails pulled off with a pliers? Hard to say. Fact is that I did with the availability of tickets back then and the fact that Lambeau was 22 miles from where I grew up, almost a straight shot up County PP - again, geography. Truth be told, I always had a back up team in the 70's for the playoffs (because the Pack were NOT gonna be in the picture) - that would be John Brodie, Gene Washington, Hank Krueger and the 49'ers. Not because of geography - because of their colors and short passing game that set up Washington for their beautiful "post patterns".
So, the fans of teams that are today's cesspools and steaming hot piles of dog crap are probably saddled with the same issues - geography and birth-right. It's all they've known and I respect that. When our run of good fortune meets the cyclical end-game that is inevitable - I'll still be a Packers guy. A good number of today's Packers fan will probably abandon ship, i speculate ... because it'll mess up their plans for the upcoming Madden release AND they'll need to be associated with a winner - it's human nature. As I said, I'll still be Packers guy because Grandpa, Dad, buddies Jack and Scottie, Coaches Don, Al, Coach Richard (couldn't say "Di(k", Glen and Bob ... Cousin Monseigneur Bob (thanks for the tix, Sky Pilot) and Father Ray ... would be haunting my sorry keester from the grave.
Geography and birth right, brothers. Glad to be here versus one of the concrete jungle metro areas.