According to a study, the Patriots have the most loyal fanbase out of the entire league. I'm sure most naysayers will state that the Patriots' fans are composed of people who grew up during the Super Bowl era, as well as bandwagoners who hopped on board during the dynasty. It appears that the connection between team and fans runs much deeper.
The other teams that round out the top 5 most loyal fanbases in the NFL are the Steelers, Colts, Packers and Jets. I'd question the correlation between "loyal" and "winning" as the majority of the top teams have had enormous success in recent years- and that goes for all of the sports evaluated.
Another good sign for New England fans is that the Red Sox (3rd in MLB), the Celtics (4th in NBA) and the Bruins (4th in NHL) all make the top 5 of their respective sports for fan loyalty. It appears teams in the Boston area have the best fans. No surprise. The cities with the next most fan bases in the top 5 are Philadelphia (Phillies, Flyers), New York (Yankees, Jets) and Los Angeles (Lakers, Dodgers) with two teams in the top 5.
I guess it's confirmed- Boston fans are the best and there's a metric to prove it.