Now, I could list a million reasons (the food, the subway–I'm a sucker for mass transit in train form, the artistic undercurrent to the city, the general hubub, the history, etc). But here's what the clincher really is for me: the people. Everyone talks about how rude New Yorkers are, that they're blunt and just all around not very nice. I found this to be completely not true. Maybe it's because I was expecting the worst and I'm a fairly to-the-point person myself, but I found people to be generally pleasant (anyone I greeted returned the nicety, I saw subway seats given to pregnant ladies, people helped each other with strollers on staircases).
Giving it even more thought (I know, really, I need a hobby), I realized it comes down to this: it's not that New Yorkers are rude, it's that they MIND THEIR OWN FRIGGIN BUSINESS. Honestly, it was refreshing to cut the small talk for a while.