F-18s would be an excellent aircraft for the Ukraine Air Force.
Armament would include Aim-120s, Aim-9X, JDAMs, HARMs, and HARPOONs.
One capability that F-18s would have that F-16s would not have is buddy refueling.
With air refueling, F-18 could have enough fuel to intercept and shoot down Bear bombers over the Caspian sea.