the Detroit Lions
According to the Pro Football Hall of Fame, as of the start of the 2007 season the team with the best all time regular season winning percentage was the Miami Dolphins whose all time regular season record was 368-252-4 for a winning percentage of .593. Second was the Chicago Bears with an all time regular season record of 670-482-42 for a winning percentage of .579.
In MLB as of the start of the 2009 season, the lowest regular season winning percentages are: 1) Tampa Bay Rays: 742-1037 .417 2) San Diego Padres: 2933-3421 .462 3) Texas Rangers: 3570-4059 .468
Highest Winning Percentage, Regular Season Miami Dolphins .580 Highest Winning Percentage, Overall Dallas Cowboys .577
Coming into the 2008 NFL season Roethlisberger's regular season winning percentage was 70.9%. Through the Baltimore Ravens game on December 14, 2008 that percentage had increased to 72.1%. He is 5-2 in the post-season giving him an overall winning percentage of 72.0% as of 12/15/2008.
According to Basketball Reference, the Lakers all time regular season record through the 2007-08 season is 2905-1824 for a winning percentage of .614.
Through the 2007 season, the American League team with the most wins in a regular season was the 2001 Seattle Mariners with 116. The American League team with the best winning percentage in a regular season is the 1954 Cleveland Indians who went 111-43 for a winning percentage of .721. Seattle's record in 2001 was 116-46 for a winning percentage of .716.
As far as winning percentage goes, the Bulldogs went 1-5 in 1904 and 1905 for a winning percentage of .167. Since they have been playing a regular season of 10 or more games, it is a .273 winning percentage (3-8) in 1953.
Yankees went 87-74 in regular season they won 87 out of 161 games .540 winning percentage.
As of the end of the 2010 season, the Detroit Lions all-time win loss record is 496-593-32 with a .456 winning percentage.
As of the start of the 2009 season, the Padres' all time regular season record is 2933-3421 for a .462 winning percentage.
Tom Osborne's regular season record in his 25 seasons as head coach of the University of Nebraska was 255-49-3 for a winning percentage of .836. His record in bowl games was 12-13 for a winning percentage of .480.
As of the start of the 2010 season, the Cowboys have leapfrogged the Miami Dolphins. The Dolphins have a win percentage of .579 and the Cowboys have a .580 percentage.