Madison Bumgarner.
Runners-up: Rory McIlroy, Breanna Stewart
The signature sports achievement in 2014 was Madison Bumgarner's October, reaching historic levels in the Giants third World Series victory in 5 years, and near mythic levels in his relief appearance in Game 7. Bumgarner wasn't baseball's best player in 2014, but in the absence of (in any sport) the best player winning the championship, it's the singular achievement of Bumgarner's October (as was also recognized by SI) that pretty clearly outdistanced the field.
I've been doing a version of this since, well, since about 1980, but it's since January of 1990 that all the records (for each month, with runners up) remain intact. Here's the list.
1990: Joe Montana
1991: Michael Jordan
1992: Mario Lemieux
1993: Michael Jordan
1994: George Foreman
1995: Hakeem Olajuwon
1996: Michael Jordan
1997: Tiger Woods
1998: Mark McGwire
1999: Tiger Woods
2000: Tiger Woods
2001: Barry Bonds
2002: Barry Bonds
2003: Lance Armstrong
2004: Peyton Manning
2005: Reggie Bush
2006: Roger Federer
2007: Tom Brady
2008: Usain Bolt
2009: Manny Pacquiao
2010: Maya Moore
2011: Aaron Rodgers
2012: LeBron James
2013: LeBron James
2014: Madison Bumgarner
