Though, capitalism is fundamentally based on concept that "greed is good", whereas other systems mainly socialism is based on "sharing". Though, sound of greed doesn't sound good, but one has to accept its one of the very basic human emotion like love, fear etc. "Greed" inculcates in us to get everything "better" and to do that we have to work harder, and if everyone works harder, the whole economy propels ahead.
Similarly, if everyone was paid the same amount irrespective of how much effort they put into something, then productivity will go down, and eventually the whole economy will bear the brunt. What incentive would there be for a person to put in more efforts.
Again, capitalism is the only system which is most tested, and if we look at the current demographics of the world, the riches countries are capitalist. You can get an idea how good the system is by looking at Korean peninsula, one country i.e. South Korea is among top 10 in GDP in world and other, North Korea cannot survive without foreign aid.
Capitalism, as a system, only fails in the areas where basic rules of economics (law of demand & supply) cannot be applied like healthcare and banking, and its where our system has let us down.
Though, it can always help from people like Bill Gates and Warren Buffet.i.e. earn how much you can in your life, but its not yours to keep and pass it on to the society.
