Its not just about the skyline bro. Its about memorable landmarks which distinguishes a city from others and makes it unique. Shanghai has a very noticeable skyline(pudong), which if you show many people in the world, they can easily recognise its Shanghai, same with New york with statue of liberty,empire state building, Times square etc, Paris with eiffel tower/champs elysees etc, Beijing with forbidden city, great wall, etc, London with london eye, Tower bridge, westminster, etc and so on and so forth.
In this respect great developed world class cities/metropolies like Seoul, Hong Kong(with its endless skyscrappers) or even Tokyo really lack this. If you show people these cities just on pic, most won't know for sure which city it is at first glance, due to they lacking a memorable/unique landmark
