There are three contenders: NY, Boston, Chicago. Nowhere else comes close (sorry, my adopted City of Angels...).
All 3 cities have major teams -- historic teams -- and a large, rabid pro fan base that extends to other regions, and many colleges.
Chicago is out. The Bulls haven't won since the early 90s. The Blackhawks have a couple of recent wins, but hockey is a niche sport. I don't know much about the Bears lately (which is a bad sign), and the Cubs.... well... let's just not. Nobody cares about the White Sox, even in Chicago.
New York, New York. It's a helluva town. If we were living in the 40s, or maybe the 60s, I'd say they were tops. But lately? The celebrated Yankees have won 1 title in the 21st century, and they're cursed with A-Roid. They're not going anywhere and the team & farm system are a mess. And with all that $$$... And the Knicks have never been good (Patrick Ewing? Carmelo Anthony? Really?). Couple of Superbowl championships for the Giants are good for them. Neither hockey team has won in forever.
Boston. They don't call it "Titletown" for nothing. Just in the last 13 years: 3 Superbowls, an NBA title, a Stanley Cup and 3 World Series. The highest concentration of colleges and universities on earth. A long, cold winter with nothing to do but drink and watch sports on TV, and a long warm summer at Fenway, the oldest park in baseball. The Celtics Dynasty of the 50s and 60s. The continuing hatred of Belichick and Brady for their perennial contender status. A 2013 Red Sox team that was in a rebuilding year and won it all. The Boston Marathon.
