A lot of interesting comments. Mostly because there is no easy answer.
To generalize:
Manhattan, the Bronx; Yankees, Giants and Rangers.
Brooklyn: Who knows? Some of them still follow the Dodgers. If they want to go to a game, probably the Mets. The Brooklyn Cyclones draw a good crowd. Brooklyn probably splits between the Jets and Giants. They may tend more toward the Rangers because they can access MSG via mass transit. They are waiting for the Nets.
Queens and Long Island: The Mets, Jets and the Islanders. Some still follow the Nets because they were on Long Island. It’s a PITA for the true Jets fans to get to the Meadowlands but loyalty wins out.
New Jersey: The Devils, Nets and whatever football team they can get tickets for. Some, especially outside the metro area, are Philly fans because they don’t want to pull for a “New York” team. That being said, they don’t have much passion for their teams.
Upstate New York: It get’s interesting. Get 100 mile outside of NYC and there is some palpable anti-City sentiment. Therefore, many will gravitate towards the Bills or even the Pats. If they do follow a “New York” team it is probably the Giants or Yankees.
As one poster mentioned, the Knicks are for masochists. A classic example of a franchise that somehow makes money while doing everything wrong. Any place other than MSG and they would be out of business. There is no rhyme or reason as to why they even have fans.
Also, it was mentioned that there are Devils fans in Manhattan. True. It used to be that it was almost impossible to get tickets to the Rangers. Hockey fans figured out they could take a bus from the Port Authority to the Meadowlands, see some great hockey, do it relatively cheaply and not worry of a DUI.
Again, no easy answer and there are thousands of anecdotes that will refute what I’ve said.