Matthew 9:12-13
12 On hearing this, Jesus said, “It is not the healthy who need a doctor, but the sick. 13 But go and learn what this means: ‘I desire mercy, not sacrifice. For I have not come to call the righteous, but sinners.”
Jesus came to save the world from itself, to save us from ourselves. I would imagine people like Moses, Abraham, Noah etc. didn't need Jesus to save them for they were already upright in GOD's eyes. Jesus came to provide a way for us sinners to reconcile with our FATHER.
One of the amazing things about Jesus' coming is that He didn't just give us a one shot deal. GOD knows that we are repeat sinners and that for us to completely abolish sin from our lives is pretty much impossible. So, GOD divised a way for us to be able seek forgiveness every time we fall.
Jesus is the ultimate physician and He provides one hundred percent recovery from our sickness of sin. His perscription is faith and trust. Through faith, we can be healed...over and over again.