God needs you. He needs you to love him, and he needs you to love your fellow men and women and help them. He has a plan for your life. It involves a loving services for him here on earth and a wonderful life together with him after death.
But we humans aren't especially loving by nature. Yes, we may be sweet and kind to our relatives and friends most of the time, but that is a long way from meeting God's demands for absolute love towards everybody, all the time.
For this is what God demands of us: Perfect, unlimited, continuous love. We can't meet this demand, and God knows it.
In most religions people have to do certain things to please the god, who then rewards them in some way. Christianity is not like that. God knows all about our inadequacy. He knows that we can't possibly meet his demands.
On the other hand, he can't relax his demands; you can't negotiate with him, and he doesn't make compromises when it comes to requiring love. Instead he has done something else: He turned himself into a human being and was born by a woman. Jesus was everything that a human being should be: Loving, helpful, caring, and completely without evil.
Here then is the most basic part of the Christian faith: We men and women deserve punishment because we are not good enough. But instead of punishing us, God let Jesus (who hadn't done anything wrong) be punished. God allowed Jesus to be tortured and executed, and in this way Jesus took the punishment that we rightly deserve.
Consider this somewhat lame picture: Imagine that you're in court, accused of driving against a red light. The judge knows you and loves you, and he doesn't want to convict you; but on the other hand he is just, and therefore he can't let you off the hook. There is only one way in which both his justice and his love can be expressed: He convicts you, but then he pays your fine out of his own pocket.
This was what God did by letting Jesus die. Through Jesus' pain and suffering, the penalty for your and my inadequacy was paid.
What remains is simply to say thank you. God made the ultimate sacrifice for your sake. Even if you had been the only person on earth, Jesus would still freely have died for your sake. Are you going to ignore this?