A misguided perception of non-New Yorkers and the belief that others are provincial because they don't live in NYC.
The idea that everything you could ever want is in NYC and there is no good reason to ever leave.
Maryland-er: I'm from Baltimore.
New Yorker: What do you mean Baltimore? I thought you were going to say Brooklyn. Baltimore? That's so far away, that's like in the middle of nowhere!
Maryland-er: Dude, it's like 3 hours from here.
New Yorker: I know! It's so far!
Maryland-er: Man, you have such a New York Mentality.