The English Puritans asked, and answered, the ultimate question this way:
Question: What is God?
Answer: God is a spirit, infinite, eternal, and unchangeable, in his being, wisdom, power, holiness, justice, goodness and truth.
- The Westminster Shorter Catechism, question four.
I think that we would be a bit more comfortable asking "who" rather than "what is God." However, would our answer be better than theirs?
Well, we would probably add the word "love." You notice that's missing in the list of attributes, although it is perhaps implied in the word "goodness." And we might change the word "spirit" to something else, since this word tends to connote ghosts (and not Holy ones) whereas the Puritans meant that God is outside this created order.
Other than that... I doubt our answer would be better. Though I admit it would be shorter.