Tiny population, long history of parliamentary democracy, very low levels of poverty, massively high standards of living, highly-developed infrastructure, incredibly liberal; basically, if you're not one of those folks who's entirely too interested in the bedroom and bodily habits of other people, it's an all-around great place to live. As long as you like rain.
Compare to somewhere like Saudi Arabia:
Big population, only existed since 1932, huge levels of poverty, wildly varying standards of living, no real infrastructure outside the cities, as uptight as a gnat's chuff about absolutely everything, dreadful human rights record, and if you're not a rich male Arabic-speaking Muslim, a right shithole in which to live.