The Length of Schedules
The length of the schedule is one of the most important differences between professional football and professional baseball. In football, teams regularly win at least 75% of their games, a record of 12-4. In baseball, the 1906 Cubs have the record for highest winning percentage ever, at .762, and are the only team with a regular season winning percentage greater than .750. The length of the schedule brings the problem of sample sizes to the league-wide level. In baseball, teams do from time to time win 16 straight games, including a 26-game winning streak by the 4th-place New York Giants in 1916. The different seasonal lengths obscure the greatness of individual teams.
In sports, as in life, flukes happen. Since the NFL went to a 16 game regular season in 1978, 5 teams have won at least 15 games in a season:
Note that 2 of the 5 teams lost in blowouts, and the only undefeated team did not win the Super Bowl. In fact, only the first 2 of the 5 teams would go on to win the Super Bowl. In a shorter season like the NFL has, especially when combined with a one-and-done playoff system, the regular season is only marginally predictive of postseason success. By adding a third round to its playoffs, baseball has achieved something similar. To wrap up, let me give a quick comparison of the above 5 to five of the greatest regular season baseball teams: