As an Ohio State fan, I always found the Michigan–Notre Dame series glorious because one of those schools was leaving with an L.
The two teams last met in 2014, a game that ended with a 31-0 Irish shellacking of the Wolverines. Though the two teams have yet to agree on a return, Jim Harbaugh is in favor of it.
From mlive.com:
"I've been on board since the inception," Harbaugh said at the Sound Mind Sound Body camp at Wayne State in Detroit. "It's something that's been working on for many months, going on seven, eight, nine months now. There are still some T's to cross and I's to dot, but I've been on board fully since the inception."
Brian Kelly is on board too, so let's hope this series comes back as soon as possible.