Baseball: NY Yankees. Been a fan since the late 1980's, so I was a fan when they stunk too.
Basketball: NY Knicks. Let's just move on, ok? Also very much loved watching the Suns with Nash and now the Warriors with Curry.
Football: New York Football Giants. Anyone playing the Pats or Cowboys.
Hockey: New York Rangers
Soccer: Liverpool FC. Haven't really followed MLS too much, guess it's the Red Bulls? Though since Gerrard is going to the Galaxy I'll watch them too.
Tennis: Roger Federer

New York doesn't really have any big college teams, so I abstain there.

Take care all.