What is the phrase describing this rivalry between two American college football teams that was ranked by ESPN in 2000 as the greatest North American sports rivalry?
1973 Ohio State vs. Michigan football game:  A conference championship, Rose Bowl appearance, and possible national championship was on the line in this monumental game, part of the hotly contested stretch of the rivalry known as The Ten Year War. Michigan–Ohio State football rivalry:  The game was ranked by ESPN in 2000 as the greatest North American sports rivalry.
The Ten Year War