For me, it is Gojira (the correct name of Godzilla).
Don't be such a snob. I can out snob you any day of the week.
2004's Godzilla: Final Wars was directed by bilingual director Ryuhei Kitamura, who went to film school in Austrailia. The movie features characters who speak both English and Japanese, so the name "Godzilla" is used throughout that movie, even though it's a Japanese movie. You can even see "Godzilla" in writing several times during the movie. They also use the name Rodan in that movie, despite the monster's name in Japnese movies being Radon.
Above and beyond that, it was Kitamura who dubbed the American Godzilla, "Zilla, because they took the 'god' out of 'Godzilla.'" And yes, the American and Japanese versions do fight in that movie, for around 14 seconds.
Don't act like you're a super-fan if you're not one. Us real super-fans are much crazier than you are.
And if you said that anybody besides Godzilla is the greatest movie monster of all time, then you're wrong and bad and not my friend.