Monotheism is a modern conception, and the word "god" originally just meant divine being. The thing that's different about Yahweh is that He's the only creator. Also, Yahweh is the only god that isn't part of a pantheon, the divine beings with Yahweh are His subordinates, they're not offspring or equals. That's much different from all the other beliefs.

Another difference is that God has a singular relationship with people. There's no give and take, it's Yahweh's way of the highway. All of the other gods rely on humans and do favors for humans if they get something in return.

It was generally acknowledged, and mentioned in the Bible, that God has a council and he addresses other divine beings--angel is a job description, the word means "messenger." Only in modern times did Jewish and Protestant leaders invent monotheism, the notion that there's only one divine being. The Bible itself notes that there are divine beings, angels, who assist Yahweh, and divine beings, demons, that oppose Yahweh, but He's the one God.