Subjective, sure but it
is based on the annual survey of living conditions. Both the Mercer Quality of Living Survey and The Economist's World's Most Livable Cities do not include entertainment and enjoyment, and for that reason some of the highest ranking cities aren't necessarily cities which automatically spring to mind as being the most desirable places to live.
i.e. Zürich (350,000), Helsinki (1,300,000), and Geneva (185,000) are often considered bland and boring in comparison to the larger cities of Sydney (5,000,000), Melbourne (4,000,000) and Toronto (4,700,000).
On and the source is
Belfast Telegraph Newslink