Divingduck--
Very subjective indeed but, IMHO (since you asked),
Europe: AMS
USA: LAX
Asia: HKG
S.America, there ain't any, it's all bad. Ditto Africa, except in South Africa.
Australia: SYD
In the LAX area for example, you have the highest concentration of general aviation aircraft in the world combined with five major aircarrier airports, and it works very well, everyday.