As far as the Bills-Sabres country goes, winning will sell.
Even if UB was a Power 5 School. If they were good and competing for National Championships, fans will show up. If they suck, the stadium/arena will be empty.
UB does draw strong TV ratings when they have a big game on TV. Last year during the NCAA Tournament, they drew strong ratings. When the Football team faced Penn State, they drew strong ratings. They will probably draw strong ratings then they face Ohio State next year. Even higher then Sabres games.
The Bills have come close to winning the Super Bowl. The Sabres have come close to winning the Stanley Cup.
The closest UB Football has come to winning a National Championship was winning the MAC Championship & Bahamas Bowl, and the closest UB Basketball has come to a National Championship was getting crushed in the Round of 32.