Ok so we've got Mars sort of figured out, let me know if people want me to change anything:
Originally there were Green Martians (DC), Black Martians (Looney Toons), Yellow Martians (Extinct), White Martians (Chituri Ultimate Marvel) on Mars. Then due to interbreeding to survive the climate of Mars, Red Martians were born.
John Carter arrived from Earth in the early 19th Century by wondering through a cave (maybe there was a rip in space that allowed him to do it). After 10 years he came back to Earth.
Then a scientist (maybe H.G. Wells' Time Travller) managed to figure out how to open the time rift, and sent a group of colonists to Mars. However, something destroyed the rift (maybe the cave collapsed or something), and the scientist disappeared. So the colonists were considered lost.
1930s or earlier, Black Martians invade Earth, having learnt about it from the human colonists, and now fear Earth is a threat, sending their disease ridden people to Mars as a potential precursor to an invasion. They are defeated by Earth (probably with disease), leaving very few of their kind left.
After the fall of the Black Martians, Red Martians and Human colonists spread over Mars, marrying and become a new species just called 'Martians'. They discover old technology, Mass Effect Relays and Aldnoah Devices (basically all the 'we found Precursor tech on mars' cliches from all the settings) making a new Empire, able to travel through space with incredible machines.
Then there is a second war with Earth. Who started it, either Earthlings in response to the early attack, or Martians trying to gain supplies, or maybe the Chitauri instigated the war as a way to find a way to take over both planets.
Possibly during this war, Martians build the
Terraformars a mutant cockroach super soldier species to fight against mankind, but they turn against them, creating a new threat on Mars. Whether this spreads to Earth and brings the Alien Engine Virus, we can decide later on.
Sometime during this conflict, or maybe after because of it, the Green Martians are driven to extinction, not by the actions of humans, but by the failure of heroes.
I think this is about as far as I got so far. Does it sound like a good outline, or any glaring problems?