Gamera 3: Revenge of Iris manages to fill - without exaggeration - every critical gap that can be found within it's two preceding films, and with flying colors. From excellent storytelling, to engaging characters, and particularly amazing effects, the movie is easily one of the very best of the genre; and easily Gamera's finest hour, cinematically and critically.
Unlike the rather formal, upfront plots of G1 and 2, G3 takes a daring leap into a far more thoughtful, perhaps even metaphorical realm; counteracting the previous installments, it features a grippingly strong cast, succeeding in creating a plot that truly depends on their actions. It blends G1's (attempt to achieve) recognizable, memorable characters into G2's flowing storyline - and from the mix comes the first of the Trilogy that feels entirely modern, well-written, and all around well-crafted.
It's almost like a portal into a political world we cannot see; one that sees Gamera not as the romanticized stereotype of a campy Kaiju, but instead as a Godzilla-esuqe 'demon' that does far more literal damage to the society around it than our skewed perspectives allow us to perceive. Through the film, I often found myself trying to discover the metaphor this argument served; however, it has become apparent that the movie is referring to itself - finally, we are revealed to the harsh realities of a hero that must destroy. Gamera is not the bright-eyed defender or action hero we've seen thus far. He is a monster - and though he has a spiritual connection to Earth, he serves his own agenda.
Iris' role as an anti-Gamera is interesting; while we are conflicted as to whether or not Gamera himself is the blessing we honor him as, Iris and his relationship with his own 'priestess' is a literal reflection of said plotline. She sees him as a hero - one set ot against the injustices dished to her and many others. We, however, clearly see the tentacled beasts' intentions - destruction and, most certainly, doomsday. He himself displays an issue with the Guardian concept tagged to Gamera; tagged to any deity. What we believe to be a shining light of hope is never without it's darkness, never without it's parallel - whether we accept it or not, no savior is without his further intentions, or, in Gamera's case, unfortunate implications.
Further, I believe there are various religious subtexts to the movie; ones of, again, unfortunate sacrifices in the name of a larger destiny, and the impact of faith. Those who actively criticize or avoid existential 'opportunities' - spare my lack of appropriate wording - may find introspective viewpoints (perhaps ones even able to expand our own knowledge), but many face a dark abandonment from the power they attack - whether it be one of societal, literal, or holy importance.
On a more critical level, not only did the entire cast carry the film beautifully, but the SPFX stood amazingly - easily the best Suitmation-CG work done, that I've seen. G2's Gamera may have been believable, but G3's fitting abomination looks nowhere near artificial; Iris, though perhaps a bit visually complicated, is just as convincing.
There are a good handful of issues; Iris is hardly explained (is he some sort of mutated Gyaos, or was that speculation?), some spiritual things were limited, the dead Gameras are a bit of a mystery, and - though the cast fit in much better than usual - there are still some members that really didn't need to be there.
Much like GMK, I find myself entranced by praise for this film - it surpasses it's brothers my miles, and is easily the best Gamera film to date.
Small edit - Lord almighty, the dub is awful for this one. The script is more or less the same, but it lacks almost all of the actual film's inflections and drama.