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).
Final Fantasy VI will always hold a special place. There tries not to be one “main” character and you get back stories and growth of most all of them (Gogo and Umaro notwithstanding). The fact that you can complete the game with as few as three or as many as all 16 too makes if very flexible in your choice of characters.