When the Bible says that 'God sent forth his son', it shows us clearly that this was a unique event — it speaks of a new set of circumstances coming into being. Jesus, the son of God, came 'in the fullness of time' - God's special time.
There are three great parts in the Bible where it says that God sent forth his son and each of them gives an important reason why this happened. In 1 John 4:10 we are told that God sent Jesus to be the means, by his death on the cross, by which God's anger and hatred against us sinners would be 'obliterated from his sight' (J I Packer). And he did this because of his love for us.
In Galatians 4:4 we are told that God sent his son to redeem us because we were slaves to sin and had broken God's law. To redeem us Jesus had to die for us to pay the price for our freedom and to bring us into a family relationship with God.
In 1 John 4:9 we read that God sent his son that we might live through him - the start of a spiritual life that never ends.
From all of this we have to see the uniqueness of God's salvation which is all centred in and achieved through Jesus Christ. We have no salvation, no forgiveness, no eternal life apart from Jesus.