I find it pretty stupid :/
"Criteria examined included life expectancy, literacy rates, school enrollment and country economies."
Well, who says just because your life is long and safe you enjoy it more than others do? It's not like you walk around every day in these top-ranked countries and praise the fact that you are not sick, have free healthcare or know that you and your friends are most likely able to read. At least I don't ..
You get a lot of depressions and suicides and you have loads of people bored with their lives in Norway too, so I basically wouldn't call it the best place to live. I think Americans enjoy themselves more than Norwegians on average, to be honest..