"First, I'd say I'm more prideful and power-hungry than greedy." (TrPrado)
I agree this is a better way to say it, but the essential point is the same. The natural human instinct is toward preservation (even aggrandizement) of self and only secondarily sympathy or altruism for others. Federalist 51, anyone? (Oh wait, Madison talked about angels. The Chairman has ruled line of thinking out of order with his "Also cut it with the god talk. Doesn't exist, doesn't matter.")
"Basically, you're right on a large scale, like the Soviet Union, but in a small community, where people can more easily know and care for each other, it has potential." (TrPrado)
Even here, motives are important. The biggest problem with socialism is its compulsory nature. But it has to be compulsory because voluntary socialism would be ripe for a free rider problem on a massive scale. (I'm not denying that there are some truly altruistic people who elevate their sympathetic attitudes above their self-advancing ones, but I think it's highly dubious to suggest that this is a natural state of affairs for any more than a small minority of people). In the small community, you can get compulsion without law through effective social pressure. Altruistic behavior becomes compatible with self-aggrandizing motives: reputation is highly important, and the expression of sympathy toward others can enhance one's reputation, thereby enhancing one's own station within the community -- if the community values such things, at least, and if a person is primarily concerned with maintaining his social standing (several important if's there). In the larger state, social pressure is much less likely to be compelling, and that's where the usual need for legal pressure comes in. In both cases, there's plenty of compulsion, and the socialist outcome, if it occurs, is less a matter of selflessness than enforced conformity.