Just making it to the 16 would make my top 5
No way. There were a lot of people on the FGC ML over Georgetown which should tell you people thought Georgetown was overrated. SDSU finished 4th in the MWC. The parody in CBB these days allows something like this to happen.
I'd say the following were way more significant...
Buster over Tyson
NYG over undefeated NE
George Mason getting to the FF
NC State winning it in 1983 only after having to beat defending champ and UNC's Michael Jordan and Virginia's Ralph Sampson in the ACC tourney just to get in the big one
Villanova over Pat Ewing and the Hoyas
Rulon Gardner defeating Alexander Karelin in the Olympics