personally i'm no agnostic, i'm a believer, and it's because of all the things i've lived and seen.
so i see this manga as a great story, and only as that, so in my opinion this isn't something you should be comparing with Jesus.
Neiher heaven or hell are in this world and that is something that many people confuse with. You are not supposed to relive a horrible moment in hell, the suffering is far more worst than that, and about heaven ... it's the total opposite, maybe not like a place where everybody is with white togas or something like that, i've really never cared about that, but a place where simply there are no more tears, no more suffering at all... a place like that... there's nothing on earth that would compare either.
another thing, the devil is not in hell... he is on earth too, and it will not be a great pleasure to him when he get send to hell either
Just a couple of clarifications maybe, but that is in my opinion why you should not be comparing it