Communism is economic system, not government type. Also i don't know what you mean by putting there 'republicanism' and 'democracy' since basically that's same word just one is greek and other is latin. So you succesfully divided votes which could go straight into one option.
Best government type is single-party cabinet if country is monocultural, and multi-party if country is multicultural since they will naturally join their kinship. Those interested in politics then join that one party, discuss matters, vote and majority proposal win, go to the legislation and become law. Just like in China, it proved to be way more efficient, both short-term and long-term.
----
If a game is around long enough, people will find the most efficient way to play it and start playing it like robots