Yankees vs. Red Sox
The reason why many baseball fans say this is the best rivalry is this, the New York Yankess have the most fans. Before the Red Sox won the World Series in 2004, it is a little lopsides. The Yankess have won 26 World Series pennants throughout its history while the Red Sox won a measly 6.
If you go to California, people will say that the Giants vs. Dodgers rivalry is the best. There is more tension with these two teams in the Bay Area and in the Greater Los Angeles Area than other teams in baseball. Giants fans hate the Dodgers and so forth. Fans talking shit at each other, and you can hear fans yell "Fuck the Dodgers" at AT&T Park. And get this, there have been years that the Gians prevented the Dodgers from entering the postseason, and there is a year that the Dodgers kept the Giants from winning the season...that was in 1993 when the Giants won 103 games and yet got their asses stuck at home. Lots of spoilers, and a controversial incident when Giants pitcher Juan Marichal hit two Dodger batters and caused a bench clearing brawl involving with a Giant batter treating with a bat.
