A brief and partial list, compiled while waiting at LaGuardia for my flight to depart:
Good restaurants, especially old-fashioned diners, everywhere.
Almost anything you might need is within walking distance and available at almost any hour.
General hustle and bustle.
Dilapidation and Grime.
Semi-shabby, 3-star hotels that describe themselves as "boutique."
A certain type of New Yorker (you know the type).
Too few parks.
Neighborhoods with little sense of community.
Anonymity to the point of invisibility. (Some may consider this a good thing.)