By that logic you should become christian or muslim because these religions defeated the others in the competitions for supremacy. Maybe japan should become a republic because republicanism won the intersystem competition with monarchy, etc. The reason why you should be a socialist is not based on weather you like the soviet union or not, instead becoming a socialist is based on the conclusion that capitalism is exploitative and should end, then you can choose which type of socialism you want to defend. Soviet socialism is called marxism-leninism, but there are other socialist systems such as democratic socialism, syndicalism, libertarian socialism, DeLeon theory, etc.