The religion practiced by the ancient Greeks was very different from that of the Hebrews. In many ways, the two religions were polar opposites. The Hebrews believed in one, omnipotent, completely sovereign God. The ancient Greeks believed that there were many gods, and that these gods were not all-powerful.
The Greek gods could be thwarted by one another, and deceived by one another. Zeus, the ruler of the gods, was not completely sovereign over the other gods. For instance, he needed help fending off the Titans in Hesiod’s Theogony. Another huge difference between the Greek gods and the Hebrew God is that the God of the Hebrews was ethically predictable, and the Greek gods were definitely not ethically predictable. The Hebrew God would provide positive or negative sanctions based on whether the recipient performed an ethical action or a non-ethical action. The Greek gods favored people based on whims, not because that person was ethical or not. They were fickle, exhibiting human vices and faults. The God of the Hebrews was transcendent, existing apart from the material universe. Some of the Greek gods were the material universe. The sun was a god (Helius), the moon was a god (Selene), and the dawn, the earth, and the heavens were also gods. The story of creation is very different as well. The Hebrews believed that God was the creator of the universe. The ancient Greeks believed that chaos was the source of some of the gods, and those gods were the source of other gods.
There are, however, some similarities between the religions. The Hebrews and the ancient Greeks both believed that deities must be appeased by animal sacrifices, and they both built temples to honor their God (or gods).