Perhaps the BEST B1G Forum anywhere, here at College Football Fan Site, CFB51!!!

Still going E->W, now the B1G-W:
Purdue:

• 86 games, Notre Dame
• 26 games, Wabash
• 24 games, DePauw
• 13 games, Miami, OH
• 10 games, Washington
• 9 games, Missouri
• 8 games, Fordham
• tie 8 games, Butler
• tie 8 games, Ohio
• tie 8 games, Ball State

Northwestern:

• 47 games, Notre Dame
• 19 games, Duke
• 17 games, Beloit
• tie 17 games, Lake Forest (Note that Lake Forest was almost a conference rival and these games were all played in that era)
• 11 games, Syracuse
• 9 games, Miami, OH
• tie 9 games, Missouri
• 8 games, Northern Illinois
• tie 8 games, Iowa State
• 7 games, Rice
• tie 7 games, Stanford
• tie 7 games, Pittsburgh

Illinois:

• 24 games, Missouri
• 13 games, USC
• 12 games, Notre Dame
• tie 12 games, Syracuse
• tie 12 games, UCLA
• 11 games, Washington
• 10 games, Stanford
• tie 10 games, California
• 9 games, Washington, MO
• tie 9 games, Butler

Wisconsin:

• 36 games, Marquette
• 18 games, Lawrence
• 16 games, Notre Dame
• 15 games, Beloit
• 13 games, Northern Illinois
• 11 games, UCLA
• 10 games, UNLV
• 9 games, SoDakSt
• 7 games, Hawaii
• tie 7 games, Iowa State
• tie 7 games, USC

Iowa:

• 60 games, Iowa State
• 24 games, Notre Dame
• 16 games, Northern Iowa
• 13 games, Arizona
• 12 games, Cornell, IA
• tie 12 games, Oregon State
• 9 games, Northern Illinois
• tie 9 games, USC
• tie 9 games, UCLA
• tie 9 games, Drake

Minnesota:

• 26 games, Iowa State
• 20 games, North Dakota
• 17 games, Washington
• 13 games, Grinnell
• 12 games, Pittsburgh
• 11 games, Ohio 
• tie 11 games, South Dakota
• 9 games, Missouri
• tie 9 games, Carleton
• 8 games, NoDakSt
• tie 8 games, USC

Nebraska:

• 109 games, Kansas
• 101 games, Iowa State
• 96 games, Missouri
• 95 games, Kansas State
• 86 games, Oklahoma
• 68 games, Colorado
• 43 games, Oklahoma State
• 24 games, Pittsburgh
• 16 games, Notre Dame
• tie 16 games, South Dakota

You are counting bowl games too I assume.  Would kind of be interested to see scheduled games.

It would be interesting but it would also be a lot harder to compile.  I just used Stassen's "all opponent" list sorted by total number of games.  It isn't perfect but it is reasonably close.  Actually I was thinking that doing one for post-WWII would be interesting because it would eliminate "rivals" from a century ago that nobody cares about anymore.  

Yeah, another good point.  MSU's second most common opponent is Marquette, with 21 games, but none since 1955.  Their 21 meetings did all come between 1933-1955 with a 2 year was break in 1943 and 1944.  So that was a legitimate annual rival...but they haven't played in 60+ years now, with Marquette dropping football in 1960 due to sadness over not playing MSU (MSC) anymore.
Marquette did play in a Cotton Bowl in the 30s.

What are your thoughts on my proposed cut-off of 1946?  My thinking is twofold:

• WWII was a major traumatic event and a lot of things changed because of the war and it's aftermath.  
• 72 years almost completely encompasses "living memory".  Ie, if a school had a "major" rival more than 72 years ago almost nobody alive remembers it.  

My concern is that almost any cut-off would be at least somewhat arbitrary and anyone could look at it and criticize it on that basis.  

Looking at two examples:
Ohio State:
Using 1946 as the start date eliminates Ohio Wesleyan and Oberlin.  Ohio State last played Wesleyan in 1932 and last played Oberlin in 1922.  Both were very important rivals in the early, pre-conference era of Ohio State football but since the Buckeyes started competing in the Western Conference in 1913 these rivalries have been largely irrelevant.  Also, 1922 was 96 years ago and even 1932 was 86 years ago it is unlikely that more than a handful of people have any recollection of Ohio State games against those teams.  

Michigan State:
Using 1946 as the start date eliminates Detroit Mercy and Wayne State.  Detroit Mercy was an annual rival from 1927-1934 during which time the Spartans went only 2-5-1 against them then there was one more game in 1960 which MSU won.  MSU played Wayne State almost every year from 1936-1946 (all but 40 and 43) and went 9-0 against them.  

Notre Dame is on the list 9 times. Syracuse and Missouri both show up on 8 of these lists.
Should frequency of conference play be consideration for acquisition? 

Notre Dame is on the list 9 times. Syracuse and Missouri both show up on 8 of these lists.
Should frequency of conference play be consideration for acquisition?

I don't want any of those teams, so by reverse reasoning from my preferred conclusion...
...no.

I can just picture Rutgers vs Princeton as being the only game of football for 56 years, lol.

Was Oho St vs Pitt ever a thing?  Seems like it could be.

Case???

I recall OSU and Pitt playing a couple times in maybe the late 90s.  They were not good games.

I'm surprised OSU and WVU haven't played more.