First, history has shown that, in the extreme, both of these constructs can have negative, catastrophic consequences. The recent economic crisis has shown what can happen when individual opportunity and greed overtakes concern for the greater good. At the other extreme, Marxism and the socialist system have many laudable ideals. However, a completely socialist system kills individual creativity and initiative and has not survived in Eastern Europe or the Soviet Union.
Thus one can argue that we need both constructs in place. The question remains: is one more important? It seems that enlightened individuals can move society forward, such as Abraham Lincoln (and, hopefully, Barack Obama). Unfortunately, other individuals, such as Adolf Hitler, can create atrocities that are inexcusable. A system built only on individual freedoms leaves too much at risk. The wrong individual could start a nuclear holocaust. Societies, and societal systems, can protect the individuals that live within those systems. The "greater good" should prevail. The challenge of any group is to encourage individual freedoms. The enlightened society will do this. The security of welfare, and, therefore, societies, are more likely to move the individual forward and mankind, in general, than the reverse.