I just don't see how anyone can ignore the Carlisle Indian School team of 1911.
(Wikipedia) In 1911, the Indians posted an 11–1 record, which included one of the greatest upsets in college football history. Against Harvard, Thorpe scored all of the Indians' points in a shocking upset over the period powerhouse, 18–15. The only loss for Carlisle came at the hands of Syracuse the following week, 12–11
Not for nothing, but back in 1978 I was the starting defensive end (speed not size) for the undefeated Intramural football champions at Oswego State. We went 6-0 in the regular season scoring 146 points and only giving up 6. Then went 3-0 in the dorm championships and, as two touchdown dogs, beat the three time defending champ fraternity winner.
Easily one of the top ten collegiate teams of all times.