Goku changed and matured the most. Early DB to post-Kami training to Saiyan Saga to Buu Saga represent four distinct stages in his character development. What Super and the internet did to him is both a crime and highly non-canon.
Pre-TS Luffy is the most mature and nuanced of the three MCs, and he arrives on the paper already formed, an almost static character. The iconic moments with Nami and the strawhat, with Hiluluk's flag, with Gaimon's treasure chests show a very unique personality, less the shounen archetype and more a 3D person.
Naruto, too, has a full arc: from loud extrovert veering on bullism in search of attention, to someone accepting his burden and responsability (and turning more introverted and prone to anxiety attacks), and becoming a guardian of his people but always prioritizing pacifism (talk no jutsu).
Goku > pre-TS Luffy > Naruto
But if we are to consider current Luffy, then he falls in last place. Everything the Marineford Saga had going on for his character got flanderized during the early post-TS arcs, then completely shat on in Wano, Egghead (VP's dead body scene), and now in Elbaf with the hissy fits about Shanks being badmouthed.