Without evil and suffering, there really can't be good. So in order to stand for good, you have to have some evil lying around. Evil must precede good because good is simply the stand against evil. Evil is more defined... suffering, malevolence, death, torment, sorrow, etc. Good is whatever counters these things. Historically if you look at descriptions of afterlife... we have an unlimited imagination for our hells and underworlds, but only a vague notion of Heaven... Heaven is mystery to us in this mortal coil. We understand Hell because it reflects our toil (%@%@% Did I just write a poem?).
Not being much the type to accept religious answers, I think we grew into the altruistic, social species we are as a reaction to the evil around us. We always strive for perfection, an escape from the shadows of Hell around us.
The Norse religion summed it up best. Evil was destined to win. The gods and the righteous dead would fall to the giants at Ragnarock... but that did not mean it was right to stop fighting for good. After the fall would be a new beginning after all (Not another friggin' rhyme!)

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"It's never over... BOY!"
The Tall Man, Phantasm III