If Jesus had never been born, we would not know that God is love. We would know some things about God that we could learn from the Old Testament, but the Old Testament tells us much more about what God expects of us than what He is like. We know His laws; we know what happens when we break them; we know how hard it is not to break them; and we know that He pretty much expects the impossible.
We would probably be either like the Pharisees who reduced the law to a bunch of nitpicking irrelevant details that they could nevertheless perform, or like the publican sinner walking around, perpetually guilty and hoping for the mercy of God, with no guarantee that they would get it.
We wouldn’t know that God was kind and compassionate. We wouldn’t know that God was tenderhearted and forgiving. We would know far more about the hard side of God than the soft side, and we would have little confidence around Him.
We wouldn’t know that God especially loves children, that He is partial towards the poor, and that He has a special place in His heart for orphans and widows.
We wouldn’t know that God deeply desires a relationship with us — that He wants to walk with us and talk with us — that, indeed, we were made for this reason. We wouldn’t know how much like Him we are, and how much like us, He is.
Jesus is all of God in human form (Colossians 1:15). That’s a great deal of communication we would have missed. Watch Jesus and we know what God is like. Listen to Jesus and we are listening to God. But without Jesus, God would be distant. Jesus brought God near. Without Him being born, God remains far away, vague, cloudy, uncertain. There is a lot of God that remains a mystery even with Jesus being born, but without that, we would be guessing as far as God is concerned.
We wouldn’t know that God weeps over us — that He wants to gather us to Himself like a mother hen gathers her little chicks. We wouldn’t know that God is willing to touch those who are unclean — that He desires to make us whole — that He cares when we are hungry. We wouldn’t know that He understands what it means to be tired, thirsty, lonely, frustrated. He knows what it means to suffer. And most importantly, we wouldn’t know that God understands what it is to be tempted in every way in which we are tempted. Yes, He understands even that.