If I Made a Godzilla Trilogy
If I ever wrote a Godzilla movie trilogy, these would be the plots.
Movie 1
In the 1950's, in fear that The United States of America might use another nuclear bomb on them in possible future wars, Japan started conducting nuclear tests to produce a counter-weapon. These tests on a nearby island cause a well-preserved dinosaur to breathe new life and is mutated into giant size by later tests. It hides underwater, sleeping until present day. After awakening from it's hibernation, it travels through Japan, leaving a path of destruction in it's wake. The Japanese notify all other countries, dubbing the monster "Gojira".
After Japan's warning that it's path would take it right through The US, they start work on a secret military project. Other countries, giving the monster the name "Godzilla", all separately try to kill it with their military might, failing every time. Godzilla destroys famous landmarks, such as the Eiffel Tower and Big Ben, as it trudges through Asia and Europe. By the time it gets to America, they've long finished their project. Godzilla destroys New York and makes it to DC, where the military first uses "Project Mogeura", a giant robot used to fight Godzilla. They fight, but Mogeura loses easily.
Learning from their mistake, the US military designs and builds a new robot based on Godzilla with better defensive and offensive capabilities, calling it "Project Mechagodzilla". Godzilla makes it to California, and that's where it faces Mechagodzilla. The two fight, evenly matched, destroying much of LA in the process. But, in the end, Godzilla is too powerful, and destroys Mechagodzilla. It makes it's way to an island, being followed my choppers. There, the military discovers that Godzilla was drawn to this place by the presence of two monsters, Anguirus and Rodan. The world silently prays for humanity.
Movie 2
The world's scientists are called to make monsters to fight the three on "Monster Island". They start testing on insects to make controllable monsters. This information is kept classified, but a leak causes outrage among many of the world. Protests and riots start from even the thought of making even more monsters. The scientists ensure everyone that they know what they're doing and everything is going to be fine, but three mutants, Kamacurus, Kumonga, and Megaguirus escape to Las Vegas and start to destroy cities and kill people. The residents of Monster Island feel the presence of more monsters, and go to see what's up.
They are immediately attacked by the insects. Kamacurus and Kumonga are killed easily by the combined might of Godzilla, Anguirus, and Rodan, but Megaguirus is a different story. After a long, grueling battle, Megaguirus dies, and the three monsters are badly wounded. Meanwhile, humanity has to deal with a long-abandoned project by Dr. Serizawa, the Destroyers, crab-like monsters that the military attempt to destroy. After Godzilla, Anguirus, and Rodan's victory over Megaguirus, the Destroyers merge into one monster, Destoroyah.
The battle with Destoroyah is a harsh one, in which both Anguirus and Rodan die. And with a final, decisive strike, Godzilla kills his foe. Mourning his dead friends, Godzilla solemnly walks back to Monster Island. Scientists, led by Serizawa, extract DNA from Destoroyah's dead, radiated body to create the ultimate weapon to use against Godzilla. They also watch as a butterfly lands on the monster's body and flies away.
Movie 3
While development of the "Oxygen Destroyer" is taking place, Earth gets a message from outer space. An alien race has shown interest in Godzilla and wishes to come to Earth to study him. Earth allows it, and happily greets the aliens. They are quick to make friends with the aliens, however, as they eventually send their monster, Gigan, to destroy humanity, and plan to use Godzilla as their own monster. Godzilla attacks Gigan once it arrives at Monster Island, though, and their battle leads them to Tokyo. The world's combined forces start an aerial battle with the aliens.
After a while of fighting, Mothra, mutated from Godzilla's battle with Destoroyah, comes to help. Realizing that the combined strength of Godzilla and Mothra will be too much for Gigan, the aliens unleash their ultimate weapon, Ghidorah. The ensuing battle leaves Godzilla wounded and Mothra dying. Mothra uses her final moments to destroy Gigan, giving Godzilla a better chance against Ghidorah. Meanwhile, the military finally gets an opening, and destroys the alien mothership, killing all of the aliens.
Without the aliens alive to control it, Ghidorah goes all out, trying to kill Godzilla rather than bring it back for the alien's use. This results in the toughest battle of Godzilla's life, fighting until he eventually blows Ghidorah's heads off one by one. Tired from the battle, Godzilla rests in the nearby ocean. The military use the opportunity to use the Oxygen Destroyer. They set it off, Serizawa killing himself in the act, and they finally kill Godzilla.