"Giant Monster Movie" separation?

What makes a movie a "giant monster movie"?

For instance, King Kong is generally regarded as a giant monster movie.
(Mighty Joe Young is much more debatable) Jaws is not, even though Jaws was
both abnormally large and at least the size of King Kong. Is it because Jaws
was not that much larger than a standard great white, whereas Kong was huge
for an ape?

Is it simply when the giantness is a plot point? If so, how large does it
need to be to be a giant monster? Would the huge shrews in Attack of the
Killer Shrews count, despite still being only dog-sized? They were
comparatively larger than Kong was.

Is it completely subjective?


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-Wolf