If the Bill shave had only one good decade ..and you can simply write off the successes of this team in 60's then by your reasoning... the Jets have had zero good decades and the Patriots have had one, the 2000's. The Fins have had two with marginally better years than we had in between.
Facts are the 80's weren't so bad when Knox stepped in. The Bills of the 90's were one of the most dominant teams ever. Few franchises have had that wit the Steelers, 'boys, Packers, Raiders, Dolphins, Broncos, Chiefs (60's) quickly come to mind. The Colts have had great teams with Manning and Johnny U but hardly dominating over a decade.
Many teams hope to have a good year or two, let alone a decade just ask the Browns, Lions, Houston, etc....