That question was intentionally worded to grab your attention, but with the utmost respect I ask again: what is it about God that makes Him great?
The pagan gods of man's imagination show their greatness in a variety of ways. Some of the gods were great because of their ability to manipulate creation. Zeus and Thor, for example, were known for creating storms and hurling lightning about. Poseidon, the god of the sea, was known for his ability to cause earthquakes and Baal was the Canaanite god who brought the spring rains. Other gods showed their greatness by their ability to destroy their enemies. Ares was the god of war who could defeat all who came against him. Hades was the god of the underworld and the bringer of death. Occasionally gods were known for their wisdom like Athena.
These are the attributes that men imagine would make a god great and, indeed, the true God exceeds the imaginations of men in all of these areas. In fact, we see that one reason for the ten plagues on Egypt was to show God's superiority: "on all the gods of Egypt I will execute judgments: I am the LORD." (Exo. 12:12, cf. Numb. 33:4). As you go down the list you see God embarrassing god after god: the Nile, a god in itself and the bloodstream of another, is manipulated by God; the cattle they worshiped were killed by plague; the storm gods could not keep Jehovah from sending the hail; the sun which they worshiped was darkened; and their death gods could not stop the final plague. About 600 years later God made a mockery of Baal in the contest atop Mt. Carmel (1 Kings 18). Jehovah was known to His people as God Almighty (Gen. 17:1, 28:3, 35:11, 43:14, etc) and God Most High (Numb. 24:16, Ps. 46:4, 57:2, etc) and there could be little question He filled those titles.
Yet it seems that God wanted primarily to be known for another trait. In Ephesians 1 we see a list of great things that God has done for us: blessed us with every spiritual blessing, chose us, ordained us to adoption as sons, provided redemption and forgiveness. Why has He done all these thing? Eph. 1:6 "to the praise of the glory of his grace, which he freely bestowed on us in the Beloved". Notice that it doesn't say "to the praise of His glory" but rather "to the praise of the glory of His grace." It seems that God is wanting to show the world the greatness of His grace and mercy. He wants the source of His praise to be not His strength and power, but rather His amazing grace.
This is a major theme of the epistle to the Ephesians: vs. 7 mentions the riches of His grace; vs 11-12 says that the Jews were made a heritage to Christ (an act of grace) "to the praise of His glory"; in vs. 13-14 the Gentiles were said to be sealed by the Holy Spirit (another gracious act) "to the praise of His glory". It seems His glory is most to be praised when we fully understand His grace. But wait . . . there's more! In chapter 2 vs 4-7 we are told we are made alive in Christ "that in the ages to come he might show the exceeding riches of his grace in kindness toward us in Christ Jesus". In other words, the entire plan of salvation was enacted to show off the greatness of God's grace! Also the church (founded upon the grace of God) made known the manifold wisdom of God (3:10) and God grants us strength and power "according to the riches of His grace" (3:16).
Over and over and over the primary praiseworthy attribute of God is His grace. His greatest works, painstakingly achieved over millennia, show off the "riches of His grace." Think about what that says about the God we serve. While He is more powerful than any pagan god imagined, more capable of defeating enemies, wiser and holier, He wants to be known for His grace. He doesn't terrorize us with threats, He courts us with mercy. Surely "the fear of the Lord is the beginning of wisdom" (Prov. 9:10), but the fulness of wisdom is shown in His greatest work of grace (Eph. 3:10). This is truly greater than any god man could imagine. Our God, who could destroy us with a word, wants to be known instead for His kindness, His long-suffering, His mercy and His grace.
Psa._84:11 "For Jehovah God is a sun and a shield: Jehovah will give grace and glory; No good thing will he withhold from them that walk uprightly"
Lucas Ward