Yes,Allah is the best Heir.
He has created everything,He is the Creator ,the Nourisher,the Loving caretaker of all.
He owns everything already and He will continue to own everything forever.This is being the best of Inheritors.
Furthermore,Allah does not need anyone to die or leave any will,to inherit the property,as it occurs among the human beings.
This also makes Him the best of Inheritors,the true Heir of everything.