One popular 'godzilla x ghidorah fanfic' is 'Clash of Titans: Godzilla and Ghidorah'. It has an interesting plot where they team up against a common enemy. The author does a great job of describing their interactions.
Another theme is the relationship between good and evil. Godzilla is often seen as a protector, while Ghidorah is more of a destroyer. Fanfics may play around with this perception, showing that there could be more to their natures. In some, they might even switch roles to some extent. This theme makes the stories more thought - provoking.
Godzilla Earth is not a fanfic. It has its own official production and creative process, distinct from fan-created works. It's a legitimate entry in the Godzilla canon.
It's really hard to say. Godzilla has his atomic breath and great strength, but King Ghidorah has three heads and can fly. In a straight - up fight, if Godzilla can get in close and use his physical strength, he might have an advantage. But if King Ghidorah can keep his distance and use his aerial attacks and energy beams from all three heads, he could be the victor.
One idea could be a story where Godzilla and King Ghidorah have to team up against an even greater threat from outer space. This would force their natural enmity aside as they realize the common danger.
I recommend Godzilla 2: King of Monsters to you. The plot is about aliens attacking and threatening Earth. At the same time, Godzilla fights with other giant monsters like Mosla, Ratton, and Kidora. In the end, Godzilla helps humans find little Godzilla and defeat the aliens with the other monsters. I hope you like this fairy's recommendation. Muah ~😗
For developing the plot, you could introduce a new, powerful enemy that neither Godzilla Earth nor the existing characters in the crossover world can defeat alone. So, they have to combine their strengths, like Godzilla Earth's raw power and the other characters' strategic thinking. As they fight together, they also face internal conflicts within their newfound alliance. Some may not trust Godzilla Earth completely, and this mistrust can create interesting sub - plots and character development. Eventually, through a series of events and battles, they overcome their differences and defeat the enemy. This could also lead to a changed world view for all the characters involved, and perhaps a new status quo for the fictional world.
One idea could be that Godzilla Earth teams up with a group of humans who have developed advanced technology to fight off an alien invasion. The humans initially fear Godzilla but soon realize they need his power.
You can try some popular fanfiction websites like FanFiction.net or Archive of Our Own. They usually have a wide range of fanfictions including those related to Godzilla Earth.