Both monotheism and polytheism tend to have a hierarchy trend located within, whereas polytheism allocates more power to the "lesser" gods and monotheism allocates more to the higher ups.
For example: In Greek and Roman polytheism, there are numerous gods for each aspect of their life, but there is usually one more powerful god, such as Zeus or Jupiter. In monotheistic christianity, there is the one God, but then there are many underling angels and Jesus, and in some cases you have the Holy Trinity which can be argued to be polytheism.
In Greek and Roman mythology, the gods were very prone to interacting with humans and feeling VERY human emotions, whereas the Old Testament and New Testament God are rather reclusive and either very angry or very benevolent.
In a nutshell, polytheistic gods usually reflect their worshippers society more, as polytheistic societies usually had a republic or democracy, with numerous important figures and one presiding figure, and the culture that christianity and old testament faith sprung out of was usually a monarchy or had some form of singular leadership.
Note: I left out Hinduism because it's hard to argue whether it's poly or mono theistic. It has a clearer main god and yet the Devas are very powerful beigns in their own right.
EDIT: I also want to include that polytheism was a quicker fix for the natural things that they were unable to explain at the time, such as the sun and moon, sea and land, etc. Now that we understand these things, we are less likely to affix a god to their existence. Though current monotheism does attribute their existence to a god, it does not attribute their constant functions, patterns, etc to the constant work of an individual god.
