I suppose you are after something like "The fate of many is sometimes determined by the choices of one or a few."
In both stories the protagonist has great responsibility since the consequences of his acts are far-reaching. Because of this, leadership is portrayed more as a responsibility and even a burden rather than a privilege: "To whom much is given much is required."
In both there is also the idea of a quest (something to be found or a challenge to be met), which is a leit motif often appearing in the epic genre.
Other common elements of the epic are a long journey or war and the story covering several generations (a saga).