Answer:
The most important feature of ancient Greco-Roman religion is its polytheistic nature, in contrast to the monotheistic nature of Judeo-Christian religion and Islam.
In other words, in Greco-Roman religion, there were many gods, godesses, and other divine beings, that were given different attributes, and worshipped accross the territory.
In fact, in some areas of the Roman and Greek Empires, some deities were more worshipped than others.
Another important characteristic is that many of the Greco-Roman divinities had human-like characteristics. They were described as deities who essentially felt human emotions and engaged in human activities.