I just saw this film for the first time earlier this year and I simply couldn't get into it. Yeah, there's enough here going for it that makes it watchable but there's still something off about the whole thing. I frankly found the human drama boring, and the special effects were definitely slapped together, especially compared to the much more imaginative Latitude Zero from the preceding year and Godzilla Vs. Hedorah the following year. It was nice to see several Golden-Age actors fill up the cast of this film, but only a few give memorable performances (namely Kenji Sahara). Even Yoshio Tsuchiya, who I absolutely admire, gives a bored performance here.
The music score is fun, and it's fun to hear Ifukube experiment with the synthesizer. But it's not one of his more memorable soundtracks, the title theme being the only piece that sticks out. The kaiju designs are really wicked cool, though. Gezora's suit is sloppily executed, but there's some strange charm to it that I frankly don't mind the head wobbling uncontrollably. The final fight between Ganime and Kameba is pretty exciting, full of great T&C action.
So yeah, not one of my favorite Showa-era kaiju films. It's got some fun aspects, but the film's just dull when the kaiju aren't on-screen. The characters are bland, and most of the cast doesn't try. I'll watch it again, but not anytime soon.