Why is Green Bay never really in the discussion for Best Team in History?

Yeah, sometimes you here they are American's Team, but when I hear people discussing the best team ever, I never hear Green Bay. They have won the most Championships (Thats what they were called before the Super Bowl) with 13 I believe. They have had there share of legends (Favre, Starr, Lambeau, Lombardi, and many many more, including the legendary Lambeau Field and Lambeau Leap)