Your righteousness, O God,
reaches the high heavens.
You who have done great things,
O God, who is like you? Psalm 71.19
O God, who is like You? What a great question! And the answer is clear. 'No one.'
Understand what our psalmist friend is doing. He is making a comparison. He is comparing his God with all of the other gods that people worship. And having made his comparison he has come to a conclusion. And the emotion with which he makes this conclusion comes through his exclamation. 'O God, who is like You?' He is simply amazed.
What is it about his God that blows the competition away? He mentions two things in this verse. First, He has done 'great things'. And what qualifies? Well, there are those 'great things' from the history of the people of God. One of the greatest has to be God's powerful rescue of His people from Egypt - where, incidentally He defeated the gods of Egypt. But there have been other 'great things' that God has done since that time. The psalmist cannot be limited to what has done in distant history. He also includes how his Lord has 'great things' in his own life. Day by day, his God has shown His power in our friend's life.
But here's another reason that the psalmist gives to explain why this God is so much better than any other god: His righteousness. The writer of this psalm is testifying to how his God has dealt with him well. He has been faithful to all of His promises. The psalmist knows, from experience, that this God can be trusted. He always comes through. Other gods also make promises. Money promises happiness. Sex promises pleasure. Marriage promises relationship. Religion promises the assurance of a pleasant forever. And these gods do keep their promises - for a time. But they are not faithful. They do not ultimately come through. They can't be trusted. But our God is different. And the exclamation fits. 'O God, who is like you?'