Okay, I can see it now: both these monsters will be minding their own business when suddenly they're both subjected to unprovoked attacks form the other. Soon, the skirmish devolves into an all-out war that threatens to trample Japan underfoot, until finally both scientists researching the situation and Gamera's child friends get in the middle, pleading with them to stop and listen.
It turns out that Gamera and Godzilla were set up to think they were enemies by the returning aliens from the third planet of the black hole, who have built both a new and vastly improved MechaGodzilla and a never-before seen MechaGamera! The two kaiju proceed to join forces to defeat their cybernetic dopplegangers and once again foil the aliens' plans for world conquest.
This is a great concept, Toho and Daiei! Feel free to use it!
I believe Godzilla wins simply because good and evil is mealiness. The world is chaos. I choose to believe Gamera trips and falls, and Godzilla tears off and swallows his head. Then he dies weeks later from an impacted bowel. Godzilla rots in the ocean and poisons the earth. We're all dead in within a year and we can never argue which made up character is more powerful than another made up character.
Mine wasn't based on power, it was based on writing themes. The good guy always wins. Regardless of the properties of the characters, the writers for such a film would write Gamera to win because he's the good guy.
Replying to old posts, joy. It doesn't really matter what Godzilla's power, strengths or abilities are. Fact is Gamera's a good guy, and that's all there is to it. Good guy always wins. Look at when Kong and Godzilla fought. While considered a tie retroactively, the film's writing definitely gave the edge and obvious victory to King Kong. Look at when Mothra and Godzilla fight. Mothra always wins. The good guy always wins, so in this case Gamera would win because he's the obvious good guy.