I'm not a believer anymore, but back when I was, I would have given you this answer:
God did not choose the Jews as a people, discriminating all other peoples. God chose Abraham, a person, not a people. And he chose him because of Abraham's qualities as a person. He made a covenant with Abraham as a person, which covered his (non-born yet) descendants. So, God was 'compelled' to stick with Abraham's descendants, due to His friendship with Abraham, not because Jews were superior in any way to other nations.
Of course, that applies if you still believe in the Abrahamic deity.