Slate calls it "a remote, primitive thing". Roger Ebert describes it as "a bad film, but with an undeniable urgency." Moria says that, although
The plot of Godzilla is substantially taken from The Beast from 20,000 Fathoms (1953), plus a little of King Kong (1933) ... it is the ferocity of Inoshiro Honda’s direction and his ability to propel the monster story to the level of metaphor that makes Godzilla an altogether remarkable film.
FilmReference.com says it
actually owes its origin to the long-held desire of special effects man Eiji Tsuburaya to make not a new and potent myth, but rather his own version of King Kong , Hollywood's most impressive monster film to date. In addition, an obvious intertextual influence was the outpouring from Hollywood's "B" producers of similar science fiction films in the American market. This trend was well established when Tsuburaya received the go-ahead from the executives at Toho Studio to make something quite similar.
DVD Talk says,
Gojira is a new kind of implacable atomic enemy: A mobile natural disaster, a typhoon in the form of a firestorm. The film grabbed the Japanese public at a gut level -- revealing a horror that had been living with them intimately for ten years, only they never knew it.