What I commonly hear is that Marx was a genius and that it was when his theories were implemented into an actual government under Lenin that there was corruption that sullied his perfect system.
I feel this is stretching the truth a great deal, because in acuality, all Marx did was copy Plato's Republic and adapt it to the labor issues of his time. Of course there was the more contemporary influence of Kant as well. Marx and Kant may seem different in their views, but they actually share many similarities.
http://ndpr.nd.edu/review.cfm?id=1445
The Republic that Plato describes from the dialogues with Socrates outlines a utopian state, but bear in mind, that was for a time in ancient history. Ancient Greek democracy was a splendid innovation, but there was already corruption and so when the question was put to Socrates on how to govern, he explored the matter philosophically. Many of the mechanisms that cause democracy to fail to bring about justice are exhibited in the story of Socrates' trial and death before the Council of 500 Athenian citizens as the jury because it shows how the elite patrician class used spin control and preyed on people's fears to manipulate the opinions of the common rabble.