Marvel

Many people are familiar with the Marvel Universe, as it is home to a number of superheroes like the Fantastic Four, the X-men, the Avengers, etc. The Universe is huge, and most of the stories center around earth. A number of galaxies have been explored in many of the pages as well, introducing a host of new species and planetary systems! Magic and High technology exist side by side. Most of the superheroes have either been altered by contact with strange substances, science or by magic to gain their power. Individuals who have developed powers on their own are known as mutants.

The world itself self is slightly bigger than earth, there are some new countries and cultures unique to Earth-616. In the distant past, the Earth-616 shared the same origin "The World of Conan". During this age when Atlantis sank its people retreated to the waters and became a new species of man, known Homo-Mermanus. It was also shortly before this time that the Eternals and Deviants were created by the Celestials, a pre-cursor to Homo-Superius aka mutants. It was only after the Great Cataclysm when the Africa, Europe, and Asia were reformed that history continues on as usual. Earth-616 also shares a "Counter-Earth" which is found in the same orbit as earth, but directly opposite from us and was never discovered.
 
What is very unique about this universe is that it contains over 20,081,205 parallel earths to date!!  The prime marvel universe in known as Earth-616. All of these parallel worlds exist within their own universe, but part of the Marvel Multi-verse. The Marvel Multiverse, is just one aspect of reality which is part of a greater continuum known as the Omniverse (DC Universe, the RPG Universes, etc). Most of these universes are divergent timelines, where certain events have altered the course of that world, however there are a number of universe that share a common theme which I will list here.


Earth-9:  This reality is aware on the multi-verse. The Dimensional Development Court has entrusted Saturnyne and the Captain Britain Corps to ensure the safety of the universe.
Earth-295: In this reality, Magneto leads the X-men as Apocolypse begins his campaign against earth.
Earth-311: Set during Age of Exploration of 1602, counterparts to many of heroes are here.
Earth-483: Wild West Era.
Earth-552: Reality where the "Blight" is taking place, planets are break downing and dying.Here Galactus is the Restorer of World.
Earth-555: Reality of the New Universal comics
Earth-597: Reality were the Third Reich won WWII.
Earth-692: The Universe created when Marvel Earth-616 and DC Earth-Prime merged.
Earth-712: Reality, also known as Earth-S where Marvel's version of DC Earth exist (Squadron Supreme).
Earth-715: Reality where female are dominant.
Earth-928: A future reality of 2099. 
Earth-982: A world were the daughter of spiderman is an active superhero.
Earth-991: Reality were America was settled by Leif Erickson.
Earth-1137: Reality were insect evolved into the dominant species.
Earth-1218: "Our" Reality
Earth-1519: World were the Aztecs conquered the world.
Earth-1610: The Ultimate Universe
Earth-1611: Where the Sentry did not dispensary from reality.
Earth-2010: Earth where vampirsm broke out globally.
Earth-2149: Reality in which the Zombie virus sprung forth. It is caught in a time loop to prevent the spread to other realities.
Earth-2301: Reality known as the Magnaverse.
Earth-7085: Reality in which superheroes were infected with lycanthropy.
Earth-7207: Reality circa the 1920s known as the Film Nior Universe.
Earth-7215: Earth in which Odin prevent man from evolving, Neanderthals dominant.
Earth-7481: Reality that follows the "Planet of the Apes" series.
Earth-8101: Reality in which Simians have evolved in place of humans.
Earth-8313: Reality that follows "Age of Conan", which is also the ancient past of Earth-616.
Earth-8311: Reality known as Larval Universe were Anthromorphic animals are dominant (Spiderham)
Earth-9105: Reality in which Egypt dominated the world.
Earth-10011: Reality in which death was defeated and opened up to the Far Realm (Shuma-Gorath, Cthulhu)
Earth-28163: Reality were mutants were the dominant species. "House of M" universe.
Earth-74101: World of an extremely male-dominated society.
Earth-70518: Earth were the conflict of WWI  continued.
Earth 91274: Reality that follows "Transformers" and "G.I. Joe" series.
Earth-93060: Reality that follows the "Malibu Comics" line.
Earth-96169: Amalgam reality were characters from "Capcom" franchise interact with Marvel Universe.
Earth-97534: Reality that follows "Anita Blake" series;