Ivo-goji wrote:^Not necessarily? This movie really is more of a sequel to Mothra than KKvsG, and Godzilla had only enjoyed top billing in two of the four films he'd appeared in so far. KKvsG though GvsM0 were essentially crossover movies featuring Godzilla rather than "Godzilla movies". Toho could very well have decided to focus on Mothra after GTTHM, if not for the fact that Godzilla had proven the more lucrative property, among other factors (being a man in a suit instead of a puppet, for instance).
Yeah, one could make the argument that Raids Again is the only true Godzilla sequel until maybe Monster Zero (since Ghidorah is more or less another crossover film), since a lot of these retroactively became "part of the Godzilla series" later on, but I can see it both ways. They're just as much "Godzilla movies" as they are "Toho crossovers".
They could have had Mothra in Godzilla's role, yeah, but that didn't happen. A giant Moth just doesn't have the same appeal as a mutated dinosaur-like creature with radioactive breath, and despite her overall popularity, Tomoyuki Tanaka knew better. Granted, she got her own short lived series 40 years later where she played that exact role, but you can imagine if there were 15 Showa Mothra films? I definitely can't. Marionettes and/or motorized worms can't emote the same way a man in a rubber suit can, especially not with '60s techniques, so it was a good call to make her a reoccurring character, instead.