In polytheistic faiths there usually is a finite limit to individuals gods. Gods can be born and be killed and therefore are not outside of the nature of time, as the monotheists believe. They have powers that are separate and individual, which means that they are not "infinite" in nature. read more
The biggest and perhaps the only necessary and sufficient reason to believe in polytheism rather than monotheism is that the former corresponds to reality. Polytheism corresponds to variety and plurality of existence in the universe, and it is honest and sincere in accepting this variety and plurality. read more