2002: Angels (99)
2004: Red Sox (98)
2005: White Sox (99)
2007: Red Sox (96)
2009: Yankees (103)
Won with Home Field Advantage: 2001, 2002, 2004, 2005, 2007, 2009, 2010, 2011, 2012
Won without Home Field: 2003, 2006, 2008 (all NL)
Average # of wins for NL Winners: 90.6
Average # of wins for AL Winners: 99
This may not be the most sophisticated way to predict the winner of the World Series, but we shouldn't ignore the patters from the past decade either. The pattern is clear: when the NL wins, the team has a relatively low number of wins and the opposite is true when the AL team wins. The team with home field advantage wins the overwhelming majority of the time.
The season win totals are incomplete, but we can get a decent idea of where it will end.
As of right now, the Red Sox and A's are losing and the Tigers are winning. If history holds, the Red Sox are probably the only one of these teams to reach the 98+ wins that AL teams have typically had. At this time, the Red Sox have to be considered the favorite. They probably would be even without the recent history, but this just add to it.
The Dodgers, Reds and Pirates all have the right # of wins, but the Pirates and Reds seem likely to play in the Wild Card game, which will put them at a disadvantage. The Dodgers seem like the most likely NL team to win.
Could it really be this simple? Maybe, for this year. The rules will be broken, but they've been fairly consistent for a while, so I'll go with it.