Serena Williams is "Sports Illustrated's" choice for Sportsperson of the Year.  The tennis great dominated the sport in 2015 winning 53 of her 56 matches and three Grand Slam titles. 

She was also the top-ranked player for every week for the second straight year.  Among the other finalists for the honor were Triple Crown-winning horse American Pharoah, soccer star Lionel Messi, MMA fighter Ronda Rousey and Golden State Warriors guard Steph Curry.