The Christian understanding is clearly misunderstood here. William Lane Craig often uses the concept that the greatest being you can think of is God. The video's author claims that he can think of a being greater than the God revealed to us in the Bible. However no proof is offered of that. And neither does the author attempt to explain by what he measures greatness. On top of all of that I see no way any one of us could come up with a more powerful, more loving, more intelligent, or greater by any measure. At the very least creating and sustaining all of reality out of nothing - energy, matter, time, space, and all there is - cannot be topped.
Debunking Christianity: Can God Exist if Yahweh Doesn't?