greatone99, I'd say that America, I'm assuming that's the nation you're referring to, is not even that close to a true democracy. You are a republic, ruled not by the will of the majority but by the law as set forth by the Constitution and judicial precedent. You elect presidents but they are not above the law. In many ways, a republic is better than a democracy because a democracy often leads to the oppression of minorities by the majority will, whereas in a republic, the rule of law can be expected to protect minorities to a degree.
I would say that most of the world's problems come simply from conflicting selfish desires and limited resources. Capitalism is the most efficient system under these circumstances... but as we see technology and productivity increasing, the resources become less limited for developed countries and they can adopt socialism.
I see communism working if you can 'cure' selfish desires, most likely through some biochemical tinkering a la Brave New World, in which people would truly be altruistic to each other. This would only be sustainable as long as it isn't exploitable by selfish individuals.
I can see communism working if the problem of limited resources were solved, whether by drastically reducing population without reducing technology through mass slaughter or natural pandemic. This would be sustainable as long as people were not very fertile, had powerful incentives against having children, or agreed not to have children, which might require a suspension of selfish desires... The same effect is achieved in small communes, but they are only sustainable as long as they can avoid conflict with other communes, especially more selfish ones.
Another way to solve limited resources is if technological growth and productivity increases outstrip population growth, most likely coupled with some sort of population control mechanism in such a way that manual labour is delegated to robots or something of the sort, and humanity becomes essentially irrelevant. This would be sustainable as long as humans did not become obsolete, say if computers became far smarter than we are, and there was no technological uprising of some sort.
All of these situations are pretty morally repulsive in my mind, though who's to say that they will be in the future? I wouldn't count on the second one ever being realized, but the first and third remain scary possibilities. We can already see this somewhat in anti-depressant medication and in the increasing trend toward socialism in the more technologically advanced nations.
I think Brave New World is much more likely than 1984.