I can't honestly think of any existing system ever that didn't end up with a small lining of aristocracy (however that was called, whether it's the aristocracy of the good ol' times of nobility, whether it's the aristocracy of the communist politburo or whether it's our aristocracy of money).
The rich do not form an aristocracy in the standard meaning of the word; in fact, capitalism was instrumental in ending the power of aristocracies in Europe.
The term "aristocracy of money" may also be used as a metaphor, to express the idea that money confers aristocracy-like benefits, but that analogy does not work, because the old saying “It is only but three generations from shirtsleeves to shirtsleeves.” holds true. Most wealthy in the US became that way without inheriting the wealth.
By the way: The system you might describe as "communist" (which I refuse to accept, it was much but certainly not communist) failed for the same reasons, oddly, that the system we live in today will fail (which I refuse to consider even remotely capitalist).
Absolutely. The commonality is the phenomena described by public choice theory. Nepotism, cronyism, abuse of governmental power exist are both a problem in our society and were a problem in all socialist and communist countries. But there is a big difference in terms of degree. In the US, that kind of corruption may account for 30% of the economy, in socialist and communist regimes, it easily accounted for 90%, and that makes all the difference: it's why we ended up wealthy and they did not. Furthermore, such corruption is part of life: you can't eliminate it entirely, and if you tried, the cure would be worse than the disease.
I'm fairly sure true communism can work. I'd still prefer true capitalism. Not because it's better, but it's far easier to implement.
That's always ever been the utilitarian argument for capitalism. Ideal capitalism works worse than ideal communism, but real capitalism works better.
But there is a second question, namely not what "works", but what kind of society we want to live in. Even perfect communism would result in a large loss of individual liberties; it's intrinsic and unavoidable.