I realize that this is Great Debates, but honestly the answer would be, “Do I want to live there?” It’s not really a metric and it’s not based on metrics.
Like, say that by being a good guy - turning the other cheek, forgiving as soon as you can, etc. - that causes greater crime in your country. But, it’s the mission statement of your country to be like that, so you just have to suck it up, because you feel that the morality of the situation demands it, or move to a different nation where they beat up suspects for confessions and have almost no crime, because you’ve decided that as a society, that’s part of the risk you take to be at risk of torture by the police but on the whole safer in your daily life.
Or say that you you live in a nation that believes there should always be support from the community - a guaranteed income, guaranteed medical care, etc. - no matter who you are nor what you contribute to society. But consequently, there’s low productivity, low rates of invention, the country isn’t very wealthy and can only provide low quality service. But maybe that’s worth it to you because you also believe that a guaranteed income, guaranteed medical care, etc. are right and that any downsides to that choice are worth it. So great, there’s a country that believes as you do. But if you don’t believe as they do, if you think that guarantees drive down the willingness of people to better the world, for financial gain, and a short-term cash grab at the expense of everyone else, well then hopefully there’s a different country that encourages people to work hard, to build up businesses, to invest in the future, etc.
I’m generally unwilling to accept the idea that certain things are better than others. Even in the case where there is no downside - I make no claims that the above examples match reality - that still doesn’t mean that the lesser options won’t be preferred by someone. To someone, living as a regular citizen in North Korea might just be the their little slice of heaven. I would personally not choose that, but I’m willing to accept that my idea of perfection is not everyone’s.
But so overall, I don’t think that there’s a best nation or a best set of metrics to judge them by. I wish that each nation had a sort of “underlying philosophy” which they genuinely worked off of and attempted to perfect themselves at (up to the point where all hell starts to break loose if it was untenable) and that it was easy for people to switch nationality easily. But I would expect the result to be, as you see today, some countries would have awful metrics but be very popular to live in (Greece, Mexico, Turkey, etc.), and others would have great metrics but be unpopular to live in (Switzerland, Singapore, Iceland, etc.). And that’s perfectly fine because we’re all different people with different beliefs.