Rodney Stark says the Greek and Roman gods were ethically challenged.
I would say probably the base of the whole thing is the image of God. The Greek and Roman gods were ethically challenged. The fact of the matter is that they didn’t care a hang about human beings, and they often mistreated them if they bothered to pay attention at all. There was no sense of virtue. And they were nasty little supernatural things – and then the Jews, and subsequently the Christians, came along with this enormously powerful, all-seeing God who was very, very much in favour of the human race. Who cared about moral behaviour but also cared about rewarding moral behaviour. Who cared what happened to humans. It was an image of God that was absolutely unique and new, and it had enormous appeal. The idea that life had meaning and purpose – this was not something that Zeus could give. And consequently the Jews before them, and the Christians subsequently, had a far more attractive, powerful, and significant God.