From the death of Alexander the Great onward, the religion of the ancient Greeks steadily absorbed foreign elements creating new forms of worship and new deities. Some examples of newly worshipped deities include Serapis, Harpocrates , Mithras, Sol Invictus and so forth.
Also in this time, influential philosphical ideas started to spread such as Neoplatonism, Alatrism, Neopythagoreanism and others.
By the time of Emperor Constantine, was the worship of traditional Greco-Roman gods (Zeus, Athena, Heracles etc) by the general population as widespread as it was in pre-hellenistic times? Or had the beliefs in these old gods become out of fashion?