Babylon is called great (Revelation 14:8; 16:19) in the same way that Jerusalem, representing all of Israel, was called great (Revelation 11:8). When "great" is used in this manner in this kind of a context, it not complimentary. The word in the Greek is megas, and it literally means "big." It can mean big or great in size, magnitude, intensity, or rank, in either a good or a bad sense. It depends on the context. This is interesting, because when God symbolically dwelt in the Holy of Holies, Jerusalem was known by its citizens as the "Holy City."
Tradition tells us (especially through Josephus) that God departed His residence there shortly before AD 70. The "Holy City" title for Jerusalem does not come back into the story-flow of the book of Revelation until Revelation 21:2-3.
In Revelation 21, the title "Holy City" is once again going to be applied to Jerusalem, but until that time, when God dwells there, it is known as the "great" city. It is great just like Babylon in its anti-God, sinful influence and economic, political, and military power. But most certainly it is not great in holiness. Israel's conduct puts its place next to Sodom, Gomorrah, Egypt, and Babylon in great defiance against God, against His message and His messengers, and thus it lost its identification as "the Holy City" and became "great."
John W. Ritenbaugh
Where Is the Beast? (Part 5)