Jesus Christ is the only son of God. He is the way, the truth and life. If you don't believe in Him then their is no need of believing in God because He is the only way to reach God.
Before He came to the world, the world was full of sin and God was so pity. For Him to save the world from sin he sent his only son that whoever believed in Him shall have eternal life.
However, when Jesus felt pain on the cross He called on the Father that why Has He forgotten Him, God did not respond due to the following;
It was the plan of God that he must die on the way of the cross for Him to save the world and whatever God has said must occur or pass through that is why it was unnecessary for him to save Jesus Christ on the cross.
Another reason is that God is pure and holy, He has no any form of impurity and hence Jesus had took all the sins of the world so as to die and resurrect for victory, God can not associate Himself with any form of sin hence He was no where to save His son.