For the Lord is great - Yahweh is great. See the notes at Psalms 77:13. This verse is taken literally from 1 Chronicles 16:25.
And greatly to be praised - Worthy of exalted praise and adoration.
He is to be feared above all gods - He is to be reverenced and adored above all that are called gods. Higher honor is to be given him; more lofty praise is to be ascribed to him. He is Ruler over all the earth, and has a claim to universal praise. Even if it were admitted that they were real gods, yet it would still be true that they were local and inferior divinities; that they ruled only over the particular countries where they were worshipped and acknowledged as gods, and that they had no claim to “universal” adoration as Yahweh has.