What do you think is the best sports city? In the US? In north america? In the world? Take your pick.
criteria is whatever you want. Championships, fans, history, etc etc.
I'll start with Boston.
Patriots/Red Sox/Celtics have all won championships in the last decade, Bruins are currently in the finals, and aside from the Bruins/a few odd seasons for the rest, each is always in the playoffs.
Fans, love em or hate em, but Boston fans are literally everywhere.
As for history...red sox, celtics, and bruins are 3 of the most historic teams in each of their respective sports.