(ignore if you aren't a Lions fan)
If the Lions meet Tom Brady and the Patriots in the Super bowl, who would you root for? Keep in mind that winning a fourth Super Bowl would allow Brady to cement his legacy as arguably the Greatest. QB. Ever. Period. Brady is a true Michigan Man and reps his alma mater as well as anyone in the league. On the other hand, if you were born and raised in the State of Michigan, chances are you rooted for the Lions growing up, watched Barry Sanders rewrite the record books without ever getting a shot at a ring, and suffered through the Millen years. A Lions Super Bowl victory might be a once-in-a-lifetime occurrence.
Personally, I would root for Brady to get his fourth ring. Brady was our starting QB for two of my five undergraduate years at Michigan, and though I've been going to Michigan games since I was a kid, my most vivid memories of the Big House are from when he was the QB. I'm nominally a Lions fan and I enjoy watching pro football, but I find it hard to get too excited about any particular team (particularly since until now, rooting for the Lions to do well was like rooting for a lifelong alcoholic to suddenly sober up). I mainly just root for Michigan players to do well.
EDIT: More context - I live in the SF Bay Area and most of my friends are annoying, smug 49er fans who think Joe Montana is the best thing that ever happened to football and that it's ridiculous to think Tom Brady is even in the same category as him. They point to the fact that Joe Montana never lost a Super Bowl and that he has 4 rings whereas Brady has 3.