What does it mean when God calls someone a "Great leader"?

Now everyone is loved by God equally; he is no respecter of persons. Nevertheless, In the bible God prophesied over certain people lives by saying they will become a great leader: I think he said that to Abraham, Moses................ These people seemed to have been the leaders of their generation, not just someone leader in the world. And I don't mean Obey God you you'll be great or follow these principles etc. These people who were called to be great leaders had an enormous stage that is admired to this day, tougher than usual trials, power, closer than usual with God. I'm just guessing or trying to make sense of what I get from it. So the term "Great Leader" in the bible really signifies what about a persons calling?