Compare this passage with 2:5-11. Christ Jesus was in the form of God but emptied himself, taking the form of a slave, being born as a human. He humbled himself and, in his obedience, accepted death on a cross.
Paul recounts his achievements and his status. Yet he is giving up those because they are no longer valuable to him. Knowing Christ Jesus is better than any thing else he has achieved.
Moreover, this achievement is not restricted to Jews only.
Lectio Divina: Philippians 3:8