Then does this mean that God is partial or prejudicial?

No. Partiality is exercised only when a party has a claim to something and does not receive it. If God owed everyone a favor, then God would be unjust to withhold from one person what he gives to another (or vice versa). Partiality is absent, however, when no one has any rights. Culpability for sin cannot be predicated of God in such instances (see, in principle, Rom 9:21–24)