They both sleep at the bottom of the ocean awakening only to terrify mankind, so they're a perfect match.
Let's be reasonable and limit ourselves to Classic Godzilla (up to and including Terror of MechaGodzilla) and pit him against Cthulhu (restricted to only Lovecraft's stories).
Godzilla:
-400 feet tall
-radioactive
-blue radiation beam
-magnetic (at least when he wants to be
![Wink :wink:](./images/smilies/icon_wink.gif)
-able to breathe in air, sea or vacuum.
-can fly (while holding one monster of equal mass)
![Exclamation :!:](./images/smilies/icon_exclaim.gif)
Cthulhu:
-very tall (anyone have a good quote that establishes his size?)
-knows magic spells to preserve life, create lightning, etc
-affects the dreams and sanity of sentients
-mastered interstellar travel
-handy T-1000esque ability to reform after massive disfigurement
-gelatinous
![Very Happy :D](./images/smilies/icon_biggrin.gif)
Which one will win?
Keep in mind that both are mortal--Godzilla died in his first appearance due to the Oxygen Destroyer and in At the Mountains of Madness, it states that shoggoths can kill members of Cthulhu's species, so they too can die.