When Is Winning Bad For A Sport?

I understand that with free agency, drafts, salary caps, etc. that this probably would never occur, but have you wonder what would happen if a single team dominated a sports league for ten, fifteen or more years? 

The Montreal Canadians won five Stanley Cups in a row, the New York Yankees won five World Series in a row, and the Green Bay Packers have won three NFL championships in a row (they did this feat twice, however they were not Super Bowls). 

The Boston Celtics won eight straight NBA championships, which is the record out of the four top sport leagues in the United States.

However, at what point would enough be enough.  When would the majority of fans give up watching a sport if a single team won every year?  How long would it take you to grow sick of it? 

A dominant team is usually good for a league.  Many people tuned in to last years Super Bowl just to see if the Patriots could get perfection in a single season.  Dominance seems to draw a crowd of people to follow a particular team to either see them win or watch them lose to an underdog. 

However, could complete dominance ever be a good thing for a sport?  While many loyal fans do not grow tired of rooting on their team who has not made the playoffs in years, I do not see them sticking to a sport that has the same result every year.  How about the fans of a completely dominant team?  Would they eventually get sick of the lack of competition?  Is that not what sports is all about; competition?

The league may step in and set new rules to even out competition.  The NHL did this when the Devils and other teams executed the trap defense so well that they made the sport “boring” in the eyes of the league desperate to attract new fans.  However, would a league take action against a team that won every championship for ten years?

Bottom Line:  You are the commissioner of, lets say the NFL, and lets say the Detroit Lions just went on a 15 straight Super Bowl Championship run, with five perfect seasons.  The TV ratings are beginning to fall and profits are not as high.  What is your solution?