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.
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.
Such novels were generally referred to as "Dungeon Fighter Online"(DnD) novels, in which the protagonist used the skills and experience of the Dungeon Fighter Online (DnD) game character to fight against the monsters that appeared on Earth. This kind of novel usually contained elements such as adventure, combat, magic, and equipment, which attracted many DnD fans.
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.
I recommend the [Starry Sky Devouring Chaos Tai Chi] to you. The main character, Zhang Junbao, was a martial arts grandmaster on Earth. Then, in the world that devoured the starry sky, he modified his martial arts, comprehended new laws, and grasped powerful strength. He would also face open-minded figures like the Sage and embark on a legendary journey. I hope you like my recommendation.
Godzilla 2002 was a Japanese movie directed by Masaaki Tezuka. It was also known as Godzilla vs Mechanical Godzilla. This sci-fi film told the story of the monster Godzilla reappearing in Japan and destroying the mechanical Godzilla to protect the Earth. The film was released in 2002 and was 88 minutes long. The main actors included Yumiko and Nobuno Itaka. According to Douban's rating, the movie received a good 6.8 points.
Godzilla 1998 was a 1998 American monster movie directed by Roland Emmerich. The film was quite different from the original Godzilla in terms of appearance and ability, and was considered disrespectful to the original Godzilla. It turned Godzilla into a fish-eating dinosaur and was eventually killed by humans with an airplane. This ending was difficult for fans around the world to accept. The film was controversial and was considered a failure.