I didn't say it was 'the best', one of the best. I get what you mean..
There are plenty of countries which I'd classify as very good, but I think Britain has traditionally had a good balance of order vs freedom, and more tolerance of different kinds of people.
I compare to other countries : I wouldn't want to live in a strict Catholic country like Poland. I wouldn't want to live in a place with the death penalty & the violent crime rate of the US. I wouldn't live in France because overall I think misogyny is entrenched there in ways it isn't to such a degree here, and I also think behavioural norms are much stricter. I read an article recently with a French designer who argued that stuff like the punks etc couldn't have come from 70s France the way they did from 70s Britain, & I think he has a point.
Maybe a Nordic country : I guess that's more a matter of climate. I like our moderate climate.
Australia and NZ? Maybe...I guess that would also boil down to climate for me, especially Oz.
I know things are fractured at the moment, but I think that applies to most of Europe. Even moderate countries like Sweden and Norway have had populist surges. Violent crime is worse here than Europe, that's a major blot. Also healthcare, education & housing need a major overhaul. Rich-poor gap is an issue across Europe, but there's definitely major challenges here now...
Sorry, that was meant to quote MrsTerryPratchett!