Before I review the importance of this film, allow me to digress.
Why is a film that incorporates CGI considered to have "better special effects" than effects done using minitures and costumes? To this point, within a couple frames:
a> You can tell "immediately" if a creature is done in CGI.
b> You can tell "immediately" if a creature is a costume.
In both cases, the effect is ineffective in that you know it's a special effect. Something either looks convincing, that is "real" and you can't identify the technique used to create it, or it does not. It's a boolean thing. Having said that, the Japanese effects >tradition< of using minitures and costumes is as equally unconvincing as CGI - however, the live action style is more vivid, and interesting. I prefer the elaborate minitures, costumes, and physical effects and find them far, far, more entertaining than something produced on a laptop with a 3D software package.
Secondly, realize that most Japanese kaiju flicks are done on a 10 million dollar budget. It was amazing in the 60's as it is now that an effects film can be realized at all with such a paltry budget. The shooting schedule of this films is also break-neck.
The reason this Gamera film is important is that it re-defined a genre. Many films and filmmakers try, few succeed. It's "The Unforgiven" (western) or The Excorsist (horror) of kaiju.
Most negative reviews of this film cite effects techniques and dubbing (it's nearly impossible to accurately dub english/japanese it's a different language, of course the lips won't synch...) These reviewer are xenophobic.
In summary, Gamera is an IMPORTANT film as it redifined an entire genre. Critics who point to effects technics and dubbing are xenophobic. Long live minitures and rubber suits! The Japanese (not the US) make the best anime and big bug, saturday matinee sci fi from the 50's to today.