I have often been asked by non-Christians (and many Christians, too) why we believe that Jesus had to die for our sins. Why would a God who is almighty require his only Son to suffer and die in a very painful way to save only those who would choose to follow him. Why wouldn't he simply snap his fingers and save the world, or, better yet, just let everyone get to Heaven. After all, he loves us unconditionally, right?
Well, the short answer to this question is that we can never fully understand God's ways. His ways are infinitely above our ways. Of course, this answer will do nothing to assuage the skeptic, so here is a longer answer:
First of all, God is just. God is Truth and God in Love, so it follows that God must be just. Would it be fair to the woman who was raped to have her killer get off scot-free simply because the judge was feeling particularly kind that day? What about the mother who lost her daughter to a murderer? No, to let the guilty go without punishment is not only unfair, but plain wrong. God cannot do anything wrong, because he is all that is good, so he must treat us, who are all sinners, with justice. (Of course, here is where we get into the argument of "Well, I am good person whether or not I believe in God, so, if he exists, he would let me in to Heaven anyway. Why do I need religion?" We all have done wrong in our lives. Sometimes the guilty simply choose not to admit their guilt out of pride and therefore sink further into it.)
Secondly, God is merciful. His mercy is plainly shown in his love for us in giving us his only Son to die on the cross for us. We had an unfathomable debt to pay (we sinned against God Almighty, an infinite being), and therefore our debt could only truly be paid in full by a divine being. So, in God's great justice, he required our debt to be paid, and in his great mercy, he allowed it to be paid by his Son, God Himself. His mercy extends to us every day when he offers us forgiveness for each and every sin if only we ask for it.
Of course, we must ask for it. This is an extension of God's justice. If a child hits his sibling and is completely unrepentant, would his father be right in ending his punishment knowing that the child has learned nothing and will likely do it again? Or must a father continue to teach his son, to plead with him to see the error in his ways and correct it? Then the full forgiveness can be extended. By the same token, if someone has spent time in jail for murder, and shows good behavior and a repentant attitude before his time is up, he may be eligible for parole.
Finally, and probably the most important: God is Love. As I mentioned before, we cannot begin to fully comprehend God's ways, and he most certainly could have chosen a very different way to save humankind. But the thing that strikes my heart the most is this: in God's great plan, he showed us how much he loves us, like no other story in the world can tell. We are human; God is divine, and yet, in his great love for us he chose to lay down his life for us. God, the infinite being, the great I Am, the one who is being itself, died for us. When we were sinners (Romans 5:8), when we were liars, and thieves, and murderers, and adulterers, when he knew we wouldn't stand up for the unborn, we would fail to feed the hungry, we would be greedy, and lustful, and lazy, we would deny the truth of God, he still died for us. He died for Hitler, Stalin, Mao, and Bin Laden. He died for many who still would not choose him, and this gave him great sorrow (the Agony in the Garden). We killed God, and he allowed us to do it so that he could show his incredible love for us--his masterpiece of creation--us poor little creatures who have the great grace to be loved by Love itself.
Since the beginning of language, we have been captivated by the great love stories, stories of kings and battles and love that endures. We understand in the depths of our souls that laying down one's life for another is the give of greatest love. This story is a part of us, and the archetype of it all is Jesus Christ, God himself. No other religion has a story of greater power and love. No other religion has an omnipotent God who is yet full of such humble love. The King stepped down off his throne to be a martyr for his people. How else could God have told his story?