Saying Allah Akbar - which means, Allah 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.
A Hadith Qudsi states, 'O My servant, I desire and you desire; you tire yourself out in what you desire and only that which I want comes to pass. Be for Me as I desire and I will be for you as you desire