...and it has very little to do with basketball and football. The top high school sport on Long Island is also the most successful program at Syracuse - Lacrosse, and that is not a coincidence.
FYI, I friend told me the NYC TV market breakdown like this - 20% Long Island, 10% CT (Fairfield & New Haven counties), 10% downstate NY (Westchester, Putnam, Rockland & Orange Counties), 20% North Jersey (as far south as Princeton, which is where the commuter rail network ends), and 40% NYC proper. He basically pulled commuter rail and bus statistics from the major transit lines (LIRR, Metro North Hudson & New Haven networks, NJT, and MTA subway). Doubt its exact; but, it makes sense.