Gamera 3: Revenge of Iris is quite unlike any other kaiju film ever made. It sees the filmmakers taking the lessons learned from their previous experiences and delivering what is possibly the most satisfying conclusion one could ask this epic trilogy.
Revenge of Iris takes the story full circle. It has the greatest strength any monster film could have, a compelling human story. This one taking a look at the impact the genre's larger than life creatures have on the world around them. Ayana and her monster Iris serve has the perfect foil against Gamera. It's a spiritual film that ultimately asks one to have faith. To have faith in Gamera and what he represents, a force of good that will never surrender no matter what.
The special effects are absolutely marvelous. I highly recommend you get a hold of some behind the scenes footage because the sheer effort and creativity at display is simple fantastic. The film has a interesting mix of cgi and practical effects that, while might not always be perfect, nonetheless delivers a sense of wonder and awe. It may have less monster action then the previous films, but the exchange is some of the most exemplary and intense monster spectacle out of any kaiju film.
Gamera 3 is a testament to the talent of its filmmakers. While they may have had smaller budgets and less resources than the Godzilla films of the time, their work on this trilogy exceeds them by far. Kaneko's trilogy is one of the most unique and well done monster films you'll ever have the pleasure of seeing.