A lot of the character of a city does come from how its citizens imagine it's supposed to be. In the nicer parts of Stuttgart in 2000: Never once even the smell of garbage.
And Copenhagen isn’t really that dense. It’s ranked 117th in the world — just under New Orleans and above Montreal: http://www.citymayors.com/statistics/largest-cities-density-...
Also thanks for adding data to this discussion, I am surprised Copenhagen ranks so low. But the neighborhoods I'm familiar with (Nørrebro, Vesterbro and Frederiksberg) definitely feel more dense than your typical North American city. The majority of housing is mid-rise, with lots of street-level retail.
That's a very shortsighted view. One can do an examination of world history and geography to strongly support the conclusion that commerce and cultural interchange has a tremendous amplifying effect on the strength of culture and the value of human capital.
Japan itself is an example of this on a smaller scale. When Europeans first got to travel in Japan, they marveled at the sheer volume of commerce they saw.
If cultural evolution is anything like genetic algorithms, then what's needed for optimal progression is a balance of interchange and continuity: multiple populations with some degree of interchange.