The Greek/Roman pantheon are poly theism, while the Judiah religions are monotheism.
It might be more accurate to say that Judaism
became monotheistic rather than
is monotheistic. There are a lot of linguistic clues in the early OT books that the Hebraic god was originally just one of the local gods, perhaps
primus inter pares, the rest of whom needed to be redacted out of later copies. It's not a settled matter, but it's an interesting hypothesis with some intriguing evidence.
And of course, by the time Christianity and Islam split off, Judaism was officially monotheistic and they carried that with them. Catholicism has gone back to polytheism since then, with three gods, one goddess, and a multitude of demigods.