Ideally, communism would be absolutely perfect - however, humans are not an ideal race, and it simply will not work correctly.
Socialism is the best political system in my mind - it allows profit, but shares it with others. However, I don't believe humans are even able for that. The ultimate state would be one which is Socialist, but chooses only certain members based on morality. How taht would be tested, I do not know, but those without regret, sympathy or empathy would not be given admission.
Star Trek's federation is perfect, but that will not happen for centuries - if ever.