Scandinavia seems to be doing all right, so that's Denmark, Finland, Norway, Iceland and Sweden for starters.
They are about as socialist as 1970s Britain
People in America scream "socialism!" whenever they hear the words "universal healthcare", so the standard in the states, at least, is really low. E.g. "Bernie Sanders is a socialist" is a common refrain even if he isn't dressed in a mao suit advocating nationalization of all private industries...that he is advocating taxing the rich more is enough.