Different ways of defining God exist. One can define God as “one who does not die.” One can define God as “the Creator.”
But a rock does not die, so does that make a rock into God? A bird can create a nest, does that make it God?
The best way of defining God is as “a being worthy of being worshiped.” This does not mean that anything that is worshiped is God. It is possible that a person could worship something that is not worthy of worship. A person might worship a statue of the Greek deity Hades. But Hades is not worthy of worship. Even those who believed in Hades saw him as the weak, misanthropic brother of Zeus and Poseidon.
Whatever we worship ought to be all-powerful or omnipotent. It does not make sense to worship something if there exists in the universe something more powerful. If something exists that is more powerful than the one we worship, then it could thwart the will of the one we worship.
Whatever we worship ought to be all-knowing or omniscient. If the one we worship is not all-knowing then there might exist someone who knows more than the one we worship. That means it could thwart the one we worship by trickery. Also if the one we worship is not all-knowing then how can we be sure it is even aware of our worship? If the one we worship is limited in knowledge, it is not worthy of our worship.
Finally, the one we worship ought to be morally flawless. It would not be right to worship a being, even a very powerful, very smart being, unless it was also good. How can we worship a sinner?
Allah is The All=Powerful (Al-Qadeer), The All-Knowing (Al-‘Aleem), and As-Salaam (The Perfect). There is nothing worthy of worship except Allah and Muhammad is His Messenger.
[Special thanks to Professor James Hall]