I disagree--I think trends have shifted away from NYC. Advertising was once largely based in NYC (Madison Ave), now Google and Facebook are disrupting that and bring it more to Silicon Valley. Mobile advertising will only further this. Finance is also no longer as loyal to NYC, look at everything Sand Hill Road has and Wall Street begins to seem less dominant. Regardless, NYC is still top-dog is many respects and will remain so for the foreseeable future, but I think this is not a fight they are going to win.
If NYC was really so much better than Boston, there would be no need to "steal" talent. You would have to build fences to keep people out.