The Superman films I envision would be a trilogy of interconnected films with a fourth movie that would continue the series onward. Ideally, the trilogy would create a foundation for a long running series of movies similar to the James Bond ones.
The first movie would be titled Superman Unleashed. The story would establish that Superman, while still relatively young, has been operating in Metropolis for a period of time already. He is working at the Daily Planet and has just started seeing Lois Lane. He is welcomed by the citizens of Metropolis and is starting become a celebrity in the city.
While he has not directly come into conflict with him yet, Lex Luthor, has been watching this new hero’s rise in his city. Lex realizes that the time will come when Superman will stand in the way of his plans, and in a preemptive move, transmits all the data he has gathered on the Man of Steel into outer space. Luthor believes that Superman is extraterrestrial in origin and that the key to his destruction may lie beyond our solar system.
The data Lex has sent out is picked up and awakens a skull shaped spacecraft that is home to the villainous Brainiac. Intrigued by the prospect of finding a Kryptonian, Brainiac rushes to Earth.
Over the course of the film, we realize that Brainiac is now the sole source of information on the planet Krypton. He claims to have saved one city on Krypton from destruction, Kandor. Meanwhile, Kal-El has grown up knowing little of his home planet. The Coluan computer helps Kal-El fill in the gaps of his home world and subsequent origin. Brainiac then attempts to recruit Superman to join him in his quest across the universe in exchange for unlimited access to Brainiac’s data on his dead planet and promise of interaction with the survivors of Kandor in their bottled city. This is a ploy however, as Brainiac is only interested in obtaining the last Kryptonian and adding him to his collection. We later learn that Brainiac exacerbated the destruction of Krypton when he captured the city of Kandor. It was also possible that Brainiac could have saved Krypton, but refused to act out of a callous apathy towards their plight.
Inevitably, Superman and Brainiac come into conflict. Brainiac has an arsenal of weapons from countless planets, including Kryptonian, to assault the Man of Steel with. Kal-El is able to overcome and defeat Brainiac before he can activate the Kryptonian super weapon, the Eradicator, upon the Earth. Realizing that Brainiac is entirely a machine, Superman dismantles him and distributes his physical body across the planet and beyond.
After the fight the military steps in to take custody of Brainiac’s ship with its assortment of technology, and weaponry. Superman takes the bottle that houses Kandor and the Eradicator weapon back to his Fortress of Solitude for safe keeping and to keep them out of humanity’s hands. A small piece of Brainiac’s tech in space reactivates, and takes off into the void of space. Meanwhile, from the shadows, Lex Luthor evaluates all of the new data he has collected on the aliens that have come to Earth.