Indeed, God commits his love for the ugly, sinful, despicably unfaithful people. Those are God's people - yes, that's you and me, too. The prophet Isaiah in ch. 54 voices God's struggle between getting angry with this people, and God's utter loving devotion to them.
Mary should be seen as a tough, gritty woman, not necessarily a beauty, not even necessarily a particularly devout person. Again, we think God must have picked her for her exceptional spirituality and pureness of faith. That may be a worthy assumption, except for the glaring fact that there is little precedent. God's choices are often ridiculous. Saul, the persecutor of Christians, called as Christian evangelist. Moses, hiding fugitive from Egypt, called to face down Pharaoh. David, a pre-pubescent not even worth considering, called to be king. Peter, a fisherman and typically abysmal disciple, called to lead the expanding church. Still think Mary was somehow qualified on human terms?
The bottom line is God's love for the unlovely, whether it's Mary or the people of Judah and Israel or us. Check out the rest in the sermon video below, and see the downloads beneath the video panel.