Quality of Life is very complicated concept. Here is several research about Quality of Life by major cities:
MERCER Quality of Life Ranking ---- Primarily targeting expatriates and companyhttp://www.citymayors.com
Top 10 are as follows. This ranking tend to prioritize safeness, education and cleanness/greenness and high cost --- thus mid sized cities do well. Among mega cities; 10. Sydney; 28. Singapore; 32. San Francisco; 34. Paris; 38. London; 40. Tokyo; 44. Barcelona; 45. Chicago; 49. NYC.
The world's top cities offering the best quality of life(New York City is the base city with a score of 100 points)
1 Vienna Austria
2 Zurich Switzerland
3 Geneva Switzerland
4 Vancouver Canada
4 Auckland New Zealand
6 Düsseldorf Germany
7 Frankfurt Germany
7 Munich Germany
9 Bern Switzerland
10 Sydney Australia
ECONOMIST Intelligence Unit Livable Cities http://econ.st/i4jhhyhttp://bit.ly/hpkxDp
Similar result as Mercer ranking, but English speaking cities do well here.
MONOCLE Quality of Life Ranking http://bit.ly/eeWpR3
So, when you consider quality of life for corporate executives and their family, mid-size cities with safeness, good education and green/cleanness tend to outperform "mega cities" such as NYC, London, Tokyo, Paris, Hong Kong, Beijing, Moskow, etc.....
It is also important to note that the cost of living and real estate price in usual suspects cities from above high quality of life ranking (such as Vancouver, Sydney, Zurich, etc..) is notoriously high.
HOW CAN CITIES WITH UNAFFORDABLE HOUSING BE RANKED AMONG THE MOST LIVABLE CITIES IN THE WORLD? http://www.newgeography.c
In fact, Portfolio.com and Business Journal has ranked quality of living by metros that include cost of living and purchasing power, Top 10 US metros are Raleigh; Washington DC; Minneapolis; SLC; Denver; Seattle; Boston; Austin Tx; San Jose CA. Megacities are not necessarily doing well. http://bit.ly/eindIq
Hope it helps!