Umm and what form did Gozer take? Oh yeah, that super scary Pillsbury Doughboy parody called the Stay Puft Marshmallow Man....
Give me a break! Yeah at certain points towards the build up to the climax the movie takes a slightly serious tone. But the payoff is a giant Marshmallow Man! Which deliberately undermines any pretense of seriousness that came before.
Ghostbusters is as Campy as the 1960s Batman tv series. Where the characters are played straight and serious to underline the absurdity of the situations they are in.