In my life I've seen interesting discussions about which JRPGs have the best protagonists and which ones have the best non-protagonist party members but I don't think I've seen this one.

Since "best" can mean anything subjective let us know what it means in your case! i.e some might choose a party based on the writing+design of the characters, others might focus on their character arcs and themes, or on the overall diversity of the party (full human teens party vs diverse ages or diverse species vs whatever Chrono Cross has going on, etc).