that wasn't equally passionate about Michigan football is lying or has never really been in a serious relationship. I've dated girls that have said "oh i'm a huge Michigan fan" and then they watch a game with me say "wow.... you're uh... really into it" and I'm like "you uh... kinda weren't".
As others have said as long as she can put up with it and let's you do your thing for 3-4 hours on a Saturday then that's fine. In the same token I wouldn't expect my wife to understand why I don't want to go to a knitting party or some other girly thing that I obviously would not enjoy (no offense to anyone who likes girly crap).
You're never going to find a girl that is crazy passionate like you about Michigan football and if you do she's 1/1,000,000 and good for you but for me it is definitely not a requirement.