How are they not different enough? They're completely different in how they play. Falco's and Ganon's properties and playstyle are completely different from their originals. And by the way, Luigi as well, is completely different to Mario and nowhere near the same as Dr. Mario is as to Mario. Dr. Mario is just a slower-stronger clone.

Have you ever actually played them instead of looking at them and saying "Yup, these two are totally alike!"