One god. Three persons. It's not polytheism. See?
I know. It's one of the tetchiest bits of Christian theology, and it requires some hand-waving.
You want to get REAL suspicious about the Christian claim of monotheism, look at the Catholic practice of venerating the saints! You can pray to them... But they're not gods. But they're there listening to and answering prayers... And they're in charge of different things... But they're not gods....
It just so happens I have a medallion of St. Isidore on my keychain. He's the patron saint of computers, computer nerds, and the Internet. I attribute my entire web consulting business to my veneration of him. But he's not a god. No, no. Hell, I'm not even Catholic.
If you want to really talk about the closest Jews have to a saint or "sub-god", by the way, it's not Moses. You gotta go Elijah.