It's actually the standard of living in communist vs. capitalist nations that proves communism is a failure.
The US today, in the midst of a deep recession, is far healthier economically than Cuba is or ever was under Castro.
I agree completely, but that goes to my second point, which was that the capitalist nations with high-standards of living during the Cold War already had high standards of living.
We have a lot of really bad test cases. Western Europe, Canada, Australia, and the United States all had high exceptionally high standards of living (based on world standards) for centuries, so it's hard to say that their success proves communism to be a failure.
The Communist nations (even Russia, which was far behind the rest of Europe before the Revolution) started at the bottom and stayed there.
And that's without dealing with countries that suffered because capitalist nations needed to exploit their labor or natural wealth (See East, Middle).
Japan might be the best example, although they had high standards of living and were aggressive capitalists before they were decimated, so a lot of the advantageous cultural, social, and political habits were already in place.
I'm not trying to argue that communism was a success, just that it's unfair to compare a government that began as a peasant revolt against an imperial power and was then carpet bombed by a superpower for a decade, Vietnam, to Australia in order to see which system works better.
The fact that every communist regime immediately crushes civil liberties is enough for me to oppose them, but in the grand battle of the "-isms" I think historical coincidence isn't given enough consideration.