First, let's stop taking things overly literal. The point of the story of the fall is that, in our earliest days, we humans rejected our relationship with God and went our own way, seeking our own wisdom, power, and glory. The whole thing about a garden, trees, the serpent, fruit, etc all serve as imagery to articulate this underlying spiritual point.
Now having understood that, what is God to do with us since we rejected him and chose to pursue evil? Our condemnation is just. Have you ever wondered what "original sin" really means? If you understand the point of the story, which I explicated above, it makes sense. Since the earliest humans rejected God, all following humans are born alienated from God and are, thereby, naturally inclined to evil. So what does God do with evil people, with his humanity who has rejected him and followed Satan instead?
That's where the Gospel comes in, which is the message of reconciliation. God, through Christ, made reconciliation with fallen humanity possible.
The story of scripture is the story of the relationship of humanity with God, how that relationship was broken, and how God is restoring that relationship through Christ, and our part in accepting this reconciliation through faith working in love.