Nowadays, probably the most popular city is New York. Nothing surprising in that, cause plenty of films and TV series were shoot in there. However this popularity has it price, literally.
Dwelling in a separate house is very comfortable. We do not need to share a wall with disturbing flatmate, sometimes we can enjoy our own backyard during summer days.
The twenty-first century means a demographic catastrophe in some areas of planet, particularly in well-developed nations where live successful people who believe at first about their knowledge paths and after about the job path rather than having a child at the age of 20.