Too be fair, couldn't exactly see Godzilla being a Green Lantern. However a Red Lantern, match but also probably the end of the world if he ever gets one. (Just in case, like how Green Lanterns are powered by Willpower, Red Lanterns are powered by rage. Considering that Godzilla attacks due to either out of anger or food, it would be more likely to see Godzilla earning a Red Ring over a Green Ring.)
In that case Green Lantern all the way. . . As long the Showa G-Man is from after the King Ghidorah first appearance of coarse. Anytime before, still have to say Red Lantern(Okay maybe except the Vs. Ebirah film), but your argument is valid.