It is interesting that market reforms in communist nations are evidence that communism is a failure, but massive government intervention to save capitalist nations, as in the 1930's and recently, are not evidence that free markets are failures.
They free the market it's proof we're right. We constrain the market, it's proof we're right.
One also has to ignore historical reality to pretend like we had an actual communism vs. free market test case. Without exception, communist countries in the later half of the twentieth century came into existence because impoverished, abused peoples revolted against their domineering power structures, whether imperial (Vietnam) or local (Cuba).
If we said today that we wanted to see if democracy worked better than communism and compared China and Iraq, I think we can be fairly certain of the result. The most powerful, best functioning nations were democratic and capitalist before the Cold War, and America was obviously not destroyed in WWII, so we were able to rebuild our allies. The communist nations started pitiful and ended pitiful.
And since we're already getting the thoughtless "you hate 'merka," nonsense, no, I'm not arguing that communism is better, just that historical fact was such that it never really had much of a chance. Russia was the best opportunity, and Stalin made sure communism would be a total failure by basically culling everyone with an IQ over 100. I'm not sure that can be attributed to "communism" the ideology, save to the extent that its structure couldn't stop abuse by tyrants.