NYC is a large city, consisting of 5 boroughs (divisions); each of which is larger in population than many US states. Its also the financial capital of the world. So just going by population alone, the NYC City Government represents more people than several state Governments. The economy of the city is also very high tech, high income etc. Although the Mayor does not have the same powers as Governor (e.g. they can't pass tax laws), he still has a lot of impact.