I have to go with Otter here.
While it is rarely overt, there are constant symbols of life/death/afterlife/heavens/hell/saviors/angels/devils, in a way that is VERY very very loosely connected to the Divine Comedies.
I've found on this forum a lot of people seemingly wary to pin any religious meaning to Mass Effect. That's really damn silly for a series that has mythological references up the yin-yang and titles like Shepard, Reapers, Cerberus, Legion, as just some of the most overt.
These are not just meant to 'sound cool'. They're supposed to be symbolic indicators without the requirement of being understood in order to understand the story. Smokingotter just goes the extra mile, just as the Mass Effect writers themselves likely did in their own way.
And yes, the layers of the ending can be compared to Earth, Hell, Purgatory, and Heaven/Paradise.
Mass Effect's whole thing is about turning things on their head though (like the original "Reapers created the Citadel in order to reap organics twist which isn't a twist by now anymore"). The 'demons' of the world (the geth, the criminals, the krogan, etc) are necessary in order to defeat the angels of death (the REAPERS). Shepard in this is a sort of redeemer of organics, whether taken from a messiah or anti-christ, or humanist standpoint.
Is this an EXACT comparison? NO. Stop thinking so. Messiah allegory exists EVERYWHERE, and often just in a tiny fraction of the amount that exists in religious texts. DON'T WORRY. Mass Effect is still not a religious game. In fact, some elements are even opposite of expected Christian norms, etc. Don't sweat it, its a story. (sorry I had to get this out of the way as I've seen the responses before)