However, God loves us and so He sent His Son in order that we could be forgiven and restored to Him so that we would not receive this punishment. This can happen because Jesus lived perfectly God's way and so didn't deserve punishment, but nevertheless He took the punishment for us by dying on the cross.
God could not abide a situation where all of mankind would be separated from Him for eternity, for He truly loves us and desires our love. So He sent His Son, Jesus, to be a man, and as a man, to be a substitute for mankind. As this substitute, He took all the punishment we deserved and offers to us everything that He deserved (i.e., life with God).
Jesus was uniquely able to take the punishment for all of mankind because He was both a man and God. As a man it was fitting for Him to be a substitute for other men and women, and as God, He was actually able to bear the punishment. It is for this reason that Jesus is truly the one way to God - it is only through accepting Jesus' offer that we can be forgiven by God and reconciled to Him. There is no other way.
The punishment for the sins committed by those who trust in Jesus was placed on Jesus - He took the punishment - therefore they can be forgiven. And since in this way those who have faith have been forgiven for past and future wrongs, they can be restored to their relationship with God.
Christ died for sins once for all, the righteous for the unrighteous, to bring you to God. (1 Peter 3:18)
Jesus answered, "I am the way and the truth and the life. No one comes to the Father except through me." (John 14:6)