The belief in "god" seems to be ubiquitous through the ages.
We know, for example, that the ancient Egyptians believed in their gods so fervently that they built massive structures like the Great Pyramid -- still today one of the largest and most enduring human constructions ever created. Despite that fervor, however, we know with complete certainty today that the Egyptian gods were imaginary. There is no evidence of their existence. Thus we do not build pyramids anymore and we do not mummify our leaders.
More recently we know that tens of millions of Romans worshiped Jupiter and his friends, and to them they built magnificent temples. The ruins of these temples are popular tourist attractions even today. Yet we know with complete certainty that these gods were imaginary. There is no evidence for their existence and thus no one worships Zeus any more.
Much more recently, we know that the Aztec civilization believed in their gods so intensely that they constructed huge temples and pyramids. In addition, Aztecs were so zealous that they were sacrificing hundreds of human beings to their gods as recently as the 16th century. Despite the intensity, however, we know today that these gods were completely imaginary. The Aztecs were insane to be murdering people for their gods. Killing a person has no effect on rainfall or anything else. We all know that. And there is no evidence whatsoever demonstrating that the Aztec gods exist. If the Aztec gods were real, we would still be offering sacrifices to them and these sacrifices would be effective.
Today's "God" is just as imaginary as were these historical gods. The fact that millions of people worship a god is meaningless.