Saying Allah Akbar - which means, God is Most Great - doesn't mean He is greater than something else, because there is nothing else for Him to be greater than.
It means that He is too great to be perceived by the senses and too deep to be understood by the intellect. Too great, indeed, to be known by anything other than Him.
Only God (fully) knows God.
- Ahmad ibn Ata'Allah
credit: inspirational sufi sayings