Given that we recognize that religion is man-made, I really think that understanding the needs that drive us to religion or hold us in it are important.  It's kind of like diagnosing common a human problem and then finding a better 'medicine' than religion for the problem.

•  Polytheism helps explain why the world is so chaotic and arbitrary by giving those attributes to the gods as a group.  Their personification as angry or capricious gods of course also makes them less admirable, but it may spread the blame for suffering around the pantheon. They can afford to have a god or two angry, because there were others to pray to for help. 
• Monotheism -  The monotheistic religions place the blame for all suffering squarely on humanity and on the 'fallen world' concept. 'God' is rubber and we are glue. Whatever bounces off of him sticks to 'us'.  I find that to be psychologically problematic.

Obviously I believe in neither.  Ultimately, as our understanding of the world grows, we have less and less need for these kind of explanations, and that is a very good thing. 

What other human needs do religion still meet that can be readily met in secular ways?