That is a fair point- although, both vs. Gigan and Zone Fighter do refer to Godzilla as 'a monster of justice'; in the latter, they specifically ask Godzilla for help and he comes to aid them, and later has friendly sparring sessions with Zone... in each case, coming when requested to render help at no benefit to himself. (And not nearly any time a kaiju shows up, either, so it doesn't seem territorial). So I do think that by the 70s, they were strongly trying to suggest that he had the intelligence and personality, rather than animal instincts, to be a hero; in some ways, I think Son of Godzilla is somewhat of a 'hero's journey' of fatherhood, too- a reluctant parent eventually coming to embrace his role, and seemingly the start of giving him more intelligent and benevolent motivations. Even if there was a self-interest angle to a number of the previous stories, that one feels like the turning point where they started portraying Godzilla of more doing things through an intelligent agency rooted in heroic sentience, which then continued through onward... although, yes, it's entirely possible to read that as people projecting onto him in everything but vs. Gigan, Megalon (where individual actions protecting JJ seem to point to more of an intentional heroic bent), and Zone Fighter, potentially.
It’s part of my secret plan to create a fifth column in the US, pre-emoting our glorious conquest and the creation of the Canadian Empire, upon which the sun will consistently set after less than eight hours of daylight.
The grace of God is a greater gift than we can truly fathom; undeserved mercy is a kindness humbling in its sheer scope.
The Zone Fighter campaign is complete, with all episodes subtitled! PM me if you need a link location.