Just because they all failed doesn't mean they did the best they could.
They never tried the best they could. They all prohibited or severely restricted cooperatives. Cooperatives are veriety and even mainstream of socialist property form. Therefore no country which prohibits socialist property form could be named fully socialist. In modern Western countries and especially in US or Canada countries like China, USSR or GDR are usually named "communist", not "socialist". And one-party rule is also usually associated with "communism". Personally for me word "communism" is rather utopic and delusional, but if they agreed to use it, this is up to them.
All countries in Europe which fell into Soviet orbit of influence copied system which existed in Stalin's USSR. Well, they had no choice. Hence one-party rule.
"Stalinism represents Stalin's style of governance as opposed to Marxism-Leninism, the socioeconomic system and political ideology implemented by Stalin in the Soviet Union and later adapted by other states based on the ideological Soviet model, such as central planning, nationalization, and one-party state
There were a few notable exceptions, however. For example in Czechoslovak socialist republic:
"In April 1945, the Third Republic was formed, led by a National Front of six parties...The Communists were the big winners in the 1946 elections, taking a total of 114 seats (they ran a separate list in Slovakia). Thereafter, the Soviet Union was disappointed that the government failed to eliminate "bourgeois" influence in the army, expropriate industrialists and large landowners and eliminate parties outside of the "National Front". Hope in Moscow was waning for a Communist victory in the 1948 elections following a May 1947 Kremlin report concluding that "reactionary elements" praising Western democracy had strengthened."