You are talking about greatness in the sense of recognition from other people or of some proprietary value. Greatness is not a value or a number or a list of achievements. Greatness is being completely satisfied with yourself regardless of anybody else's interpretation.
A bum sitting on the corner of a street has much more wisdom to offer this society than any rich man in a business suit. Wealth is not an achievement of money or social recognition. Just as a man who outcasts himself from society to fully explore the nature of himself and to understand what that truly means.
There isn't anything you have to do or achieve to be great.
You can be great by being just who you are now and truly accepting yourself without any judgments or predictions of who you should be.