"YANKEES SUCK! YANKEES SUCK!"
1918: Last World Series win for almost ninety fucking years. Bellyaching about this begins immediately after the 1919 season.
1946: Hope is briefly raised. Then crushed.
1967: Beaten by the Cardinals.
1975: Nothing Sox fans want to talk about happens this year.
1986: Bill Buckner causes a wave of suicides across the North East.
2004: Curse Reversed, Sox Fans Officially Become Tiresome
2007: Sox Fans get even more tiresome.
2008: Manny "Whiny Bitch" Ramirez gets traded just in time.
Until about 1996, the Sox and the Yankees had a fairly friendly rivalry. This was because from about 1920 to 1960, everybody loved the Yankees, and from about 1960 to about 1996, the fans could commiserate because their teams both won a lot and still managed to suck pretty hard.
Around 1996, a lot of things happened to cement that into a bitter, vile hatred fans of each share for the other. First, with the death of Ali Ramirez, the Yankees certified that being an obnoxious dipshit (i.e. a "Bleacher Creature") was A-OK as far as they were concerned. Secondly, it was right around this time that the Yankees went on what even Sox fans will admit was an epic winning streak (although, as they'll gladly point out, for about fifteen years beforehand the closest the Yankees got to the Series was selling peanuts).
Cross longtime assholes with a winning streak, which means lots of bandwagon fans and padawans in the way of the drunken idiot sports fan, and you get more douchebags in your fanbase than Summer's Eve.
As a result, in the Northeast, it will always be about the Sox versus the Yankees. It doesn't matter what happens, anywhere. Patriots fans will chant "YANKEES SUCK!" at games where the opposing team isn't even from New York.
To be fair, the Yankees and their fans had every right to be confident they were going to be back on top. After all, they'd won the first three games of the playoffs. One more and their spot, and therefore the World Series, was assured. After all, the Sox were losers and would always be losers! Let's start selling Series tickets and playoff champion shirts now! Yes, they really did that.
The Yankees and the Sox have essentially switched places. Now, Yankees fans, the ones that didn't start quietly rooting for the Red Sox once they got into the Series, search for obscure reasons like ghosts for their team's failure to win a Series in what's coming up on a decade now, including tossing grass seed around at Fenway Park hoping to create a Yankees "home field advantage" and Sox fans have become insufferable about their team's superiority. Amusingly, some Yankees fans now whine that the Sox should be called the Evil Empire.
Fenway Park is notable as one of the nation's oldest baseball stadiums, and also the one with the most ass-numbing seats in American history, all of which were removed from Tom Yawkey's secret torture chamber and have not been repaired since they were first installed. Among its other notable features are an enormous green wall called the Green Monster, which they decided to turn into a mascot that looks like a Muppet covered in Astroturf, and being located on one of the least convenient stops in the entire Boston public transit system. It's also a very, very short walk from Boston's Fenway, the city's gay district. Before you ask, no, Derek Jeter and A-Rod have never been seen going there. Together.
It has been alleged that David "Big Papi" Ortiz and Manny "Whiny Bitch" Ramirez both were taking steroids during the 2004 and 2007 seasons.
Which kind of sucks because it was cheating, but then again, A-Rod, Giambi, and Clemens were all doing 'roids and still got their asses handed to them, so in the end, it's kind of a wash.