In my opinion there is little competition for London, New York and Milan if what you are asking is a combination of well dressed men in the most stylish locations, as opposed to the badly dressed men on the streeets of any city in the world, and for shopping.
Naples is a great place to have clothes made but the local dress is not particularly stylish once you exit Rubinacci. Paris has great fashion, but well dressed Parisian men go to London for their clothes. Hong Kong copies London, and sometimes Italy, and so does Tokyo though it also has some vibrant fashion.
If the list extended to five I would probably add Madrid and Vienna.