A few scriptures will reveal the true purpose of God selecting a people to set apart on the earth-

Exodus 19:5-6:

"Now therefore, if you will indeed obey my voice and keep my covenant, you shall be my treasured possession among all peoples, for all the earth is mine; and you shall be to me a kingdom of priests and a holy nation."

Deuteronomy 4:5-6:

"See, I have taught you statutes and rules, as the Lord my God commanded me, that you should do them in the land that you are entering to take possession of it. Keep them and do them, for that will be your wisdom and your understanding in the sight of the peoples, who, when they hear all these statutes, will say, 'Surely this great nation is a wise and understanding people.'"

Isaiah 49:6:

"He says: 'It is too small a thing for you to be my servant to restore the tribes of Jacob and bring back those of Israel I have kept. I will also make you a light for the Gentiles, that my salvation may reach to the ends of the earth.'"

Micah 4:1-2:

"In the last days the mountain of the Lord's temple will be established as the highest of the mountains; it will be exalted above the hills, and peoples will stream to it. Many nations will come and say, 'Come, let us go up to the mountain of the Lord, to the temple of the God of Jacob. He will teach us his ways, so that we may walk in his paths.'"

Matthew 5:14:

"You are the light of the world. A town built on a hill cannot be hidden."

So we see that it wasn't so much like a parent having a favorite son above all their other children, but rather a son who was called to a special mission of being a good example to the others, to show them God's wisdom and cause them to desire God's ways. Keep in mind back then the idolatry and wickedness was at an insanely high level. Child sacrifice, orgies, murders and robberies, slavery, torture etc was COMMON. So Israel was to show the world a better way to exist on this fallen plane. And now that job has been transferred to Christ's church!