alt Hacker NewsHizzoner aside, I don’t think NYC’s government is markedly more crooked than any other American municipality.
(NYC news is often national news, so there’s a double effect: transparency is a deterrent, and transparency makes the city look uniquely corrupt. If, say, Dallas had the same kind of persistent national coverage as NYC does, I’d expect to see roughly the same stuff.)
NYC has a markedly more pronounced history with organized crime - including that extant sort which is associated with the financial industry - and the municipal culture that develops to deal with it. Of course, this implies that now that Dallas is getting a stock exchange, your claim might become salient in a decade or two.