His assumption is that the only greatness worth achieving is in the video game world, the kind where some hero goes off to save the world.

My assertion is that the best kind of greatness is the one where a man sacrifices in some way for another, leading to the other's betterment/rescue/etc.

So, in this sense, one could save the world very selfishly and that would be a diminished greatness compared to a son who takes a leave of absence from work to care for his dying father.