There are probably no countries in the world today which could truly be called "Socialist." To be so would require that the people owned, managed, and enjoyed the earnings of all the country's industry. A rather Utopian ideal which never has occurred in the real world, although the Communist bloc pretended its countries were so organized.
Contrary to the common misconception in the USA, Sweden is not a Socialist Country. It has one of the world's oldest stock exchanges and the ownership of businesses and industry is exchanged daily and just as robustly as on the New York Stock Exchange in the USA. Except for some minor extraction industries, and some public transportation, all Swedish businesses and industry are in private hands. Current estimate would be that over 95% of industry is in private hands, which is about where it is in the USA. The major "Socialized" industry is the health care sector. While the USA has a large socialized health care sector under Medicare and medical care for members of the Military families and for Veterans, the Swedish system is more extensive. However, the USA has a larger public transit sector.
Were I asked to speculate on which European country was the most Socialist, I would guess Norway for the simple reason that a large part of its oil and gas industry is State owned. So far the profits from that industry seem to have been directed to the general welfare of the populace.
tl;dr version: Norway, Sweden, Denmark, Iceland, Finland - these countries enjoy the highest standard of living