Superman: Whatever Happened to the Man of Tomorrow?

Superman: Whatever Happened to the Man of Tomorrow? is a Superman story written by acclaimed writer Alan Moore. It is unknown if this was cannon or not before Crisis on Infinite Earth.
Superman #423

The framing device is reporter Tim Crane asking Lois Lane about what happen to Superman. Ten years prior, Terra-Man and Parasite killed each other, most of Superman's enemies disappeared and Brainiac was seemly killed. Bizarro (whose modus operandi is being the "perfect imperfect duplicate" of Superman) went on a murderous rampage (resulting in the destruction of the Bizarro World) and killed himself (since Superman is alive). His last words are "Hello, Superman, hello." Toyman and the Prankster tortured Superman's childhood friend Pete Ross and learn of Superman's alter ego. Then, they killed Pete Ross and unintentionally revealed Superman's identity when trying to kill Clark Kent. Lex Luthor found the remains of Brainiac, which took over Lex Luthor's body when he unintentionally reactivated it. Seeking to kill Superman, Brainiac allied himself with Kryptonite Man I. After duplicates of Metallo attacked the Daily Planet building, Superman had Jimmy Olsen, Lois Lane, Lana Lang, Krypto, Perry White, Krypto and Alice (Perry's wife) retreat to Fortress of Solitude. The Legion of Super-Heroes gave Superman a golden trophy of him with a Phantom Zone projector (a device he used to trap / free people in / from the Phantom Zone) with "HIS SUPREME HOUR" written on it. They went back to the future.
Action Comics #583

Brainiac, Kryptonite Man and Legion of Super-Villains attacked the fortress. Brainiac created a force field to stop other heroes from helping Superman. Lana and Jimmy used devices in the fortress to give themselves superpowers. Lana fought Krytonite Man as Jimmy disabled the force field generator. Lex regained a small amount of control of his body and begged Lana to kill him. Lana then snapped his neck thus killing him. The Legion of Super-Villains killed Lana. Brainiac managed to take over Lex's corpse and kill Jimmy Olsen. He noted the force field is somehow still up despite Jimmy destroying the generator. Then, Brainiac launched a nuclear bomb. This bomb finally was able to breach the fortress. Kryptonite Man tried to attack Superman. However, Krypto attacked Kryptonite Man and killed Kryptonite Man to save Superman, but was killed himself. Brainiac turned off due to Lex's body entering rigor mortis. After Superman became enraged upon discovering the LSV killed Lana, they fled to the future. Superman realized one major villain is missing: Mister Mxyzptlk. He figured out Mister Mxyzptlk is the mastermind behind this. Mister Mxyzptlk appears and explained he got bored with being mischievous and decided to be evil (hence why he did this). He turned into a vaguely humanoid, monstrous form and tried to kill Superman. Lois and Superman realized the trophy is really a Phantom Zone projector. Superman used the trophy on Mxyzptlk as Mxyzptlk said his name backwards to escape. Being literally torn apart by this, Mxyzptlk dies. Superman, realizing his broke his code of never killing, used gold kryptonite to remove his powers (this was before gold kryptonite was rectoned into only sapping his powers away for 24 hours). Superman was assumed to have died in the Arctic (where his base is). In present day, Crane leaves and we discover Superman is now a mechanic named Jordan Elliot and married Lois. His son, Jonathan, displayed super powers.
References:

• http://en.wikipedia.org/wiki/Superman:_Whatever_Happened_to_the_Man_of_Tomorrow%3F