You want a time line? I'll give you the time line. I got very bored today and decided for who knows why to try and fill in the gaps once again.
[20XX]So starting out Dr's. Wiley and Light created Protoman(Blues). Dr. Wiley was a greedy man, and wanted all the credit for himself, so he stole Protoman and made some modifications, he planned on selling the design to the military and make lots of money off of it. Before he could do so however, Dr. Light became aware of his plans and created Megaman(Rock). Then some other things I'm not quite clear on happen and those lead up to the events of MM1 - Megaman and Bass.
Then after those events Dr. Wiley creates Zero, the "Super Robot" at this point in time I believe that Wiley unleashed Zero upon the world and he is stopped by the combined force of Megaman, Protoman, and Bass. They all are destroyed in the process, but the cause enough damage to Zero to cause him to flee for repairs. Dr. Wiley then seals Zero in a repair capsule.
After the Zero incident Dr. Light has nothing left that could possibly stop Zero if he were unleashed again, so he designs and constructs X. [Source:
Bonus DVD included in MMXMH for PSP (X1 remake)]
[21XX-22XX]According to video linked above, X is sealed away because his abilities would be feared by man. X is later discovered by Dr. Cain, who uses X's design to create Reploids. Dr. Cain creates Sigma, who he considers his greatest work. Sometime after that Zero's repair cycle is completed and he goes forth to do what he is programmed to do. Zero wreaks havoc on the world around him and Sigma is dispatched to take care of him. Sigma eventually defeats Zero by breaking his head gem but in doing so the Zero Virus is transfered from Zero to Sigma. The Zero Virus then evolves into the Maverick Virus. Zero was taken in for study, because he had no records of creation, he was later repaired and put to work in the military under Special Unit Zero. During all of this Sigma begins to secretly infect other Reploids and Mechanaloids spreading chaos across the world.
Dr. Cain finally figures out how to awaken X and does so. X and Zero are introduced, then partnered in the military. Thus summarizing all the events between Megaman and Bass and MMX1.
MMX1-X6 happen all in succession, but then the storyline SPLITS...Follow X's ending to get X7, X8, and Command Mission.
Follow Zero's ending to get to the MMZ series and then onto ZX. BUT I'm not done yet...oh no, it can't be easy...
So after Zero's ending in X6 he is sealed away for repairs AGAIN for 103 years. So after Sigma is defeated I believe that he comes back once more, during this time period New Type Repliods are created, supposedly they are "Maverick Proof", but that theory is smashed with the events of X8...So the events in X7 still happen, but without Zero being there. X looks for more peaceful ways of dealing with the threats and Axl is just there for filler...because let's face it...Capcom loves the filler. =__="
Sometime after this Dr. Weil enters the mix and creates the Mother Elf. It's powers to increase the ability of any Reploid by tenfold is greatly abused by the military and the people revolt.
Then the Elf Wars occur. By the way, somewhere in this time frame Zero is rediscovered by Dr. Weil and his body is replaced with a copy. His original body is then used by Dr. Weil to create the Reploid Omega in order to put an end to the war. Upon Omega's entry in the war it is discovered that he is far too powerful and X comes out of his peacful ways and defeats Omega. X then decides to take the Mother Elf and seal it in a vault and uses his body as a lock.
[23XX]Ceil, a child genious find a way to take X's consciousness and tranfer it to a Cyber Elf. Ceil, thinking she'd be doing the world a favor, decides to build a copy of X. Although a great idea, this Copy X's ideas of right and wrong aren't quite the same as the originals and he begins to "retire" Reploids in fear of them turning Maverick once more. Ciel, disgusted by what she's done, creates a resistance to Copy X and begins searching for the legendary hero, Zero. Enter the events of MMZ1's opening cutscene where she discovers Zero.
The events of MMZ1-4 take place where Zero finally dies saving the world from Dr. Weil. Sometime after this Ceil (it is believed to be her anyways...) creates the Biometals. It's not clear on what happens from here. Somehow she gets a hold of the remains of Zero, the three remaining Guardians(who suddenly disappear between Z3 and Z4, and transforms them into Biometals to honor their great service to humanity.
From there it is believed that she had no children, but Alloutte, the little girl that was found in the Resistance Base, followed in Ciel's footsteps and became a great scientist. Prairie, the current leader of the Guardians in MMZX, is believed to be a descendant of her.
[25XX]Fast forward 200 years into the future to the current time line of MMZX...Humans and Reploids now coexist peacefully.
The Federation Government, Legion, was established as an organization that helps blur the line between humans and Reploids by giving humans cybernetic enhancements and giving Reploids artificial life spans. In time, the Humanoids of Earth (who were once humans and Reploids) managed to revive some of the former nations of Earth. However, preventing further prosperity like the days of old, incidents around Earth began where some of the machine life forms became Mavericks, making some areas dangerous, and soon this activity obstructed exchange between nations.
The nations became divided into areas designated as Innerpeace, utopian-like cities where it is designated as a safe haven for Humanoids, and the Outlands, where the dangerous Mavericks, Reploids and Mechaniloids that threaten the peace, appeared. Innerpeace and the Outlands are furthered separated with designations of lettered Areas.
Great developments were made due to the efforts of the corporation Slither Inc., which possesses technology unearthed from ruins in the Outlands. Peaceful life in Innerpeace is maintained by receiving the technology offered by Slither Inc.
In the frontier regions (where the crisis management of countries still doesn't reach), damage from attacks by Mavericks still occur. The Humanoids in these areas developed a self-defense organization known as the Guardians. The Guardians defend the Outlands and investigate the cause of the Maverick attacks. The original leader of the Guardians disappeared during the investigation of an Outlands area.
Ten years prior to the game's start, the protagonists Vent and Aile lost their mothers to a Maverick raid in the Area H amusement park and became orphaned. They were taken in by Girouette (or Giro for short), the owner of Giro Express, a transporter service which will deliver anything from letters to weapons, regardless of legality.
Advent takes place four years and eight months after the events of the first ZX title. Many people known as Hunters formed the Hunter's Guild to seek the wealth inside the ruins. Meanwhile, those unwilling to join the Hunters and collect the treasure through their own means were come to be known as Raiders, and the two often clashed in their own missions to gather the buried technology.
And finally...there is the Megaman Legends(DASH in Japan) series...this is where the story gets truly messed up....Pay attention now...
[8XXX]According to the sourcebook, Rockman Perfect Memories, the Legends series takes place after the ZX series. Some have even speculated on such a connection based on comments in the X series; most notably, the use of the word Elysium (with a capital E, indicating it is a proper noun) in one of the endings of Mega Man X5. Other examples include the frequently-seen Reaverbot eye symbols that appear in Hyleg Ourobockle and Burble Hekelot's levels in Mega Man Zero 2 and Hanumachine's level in Mega Man Zero 3. There also appears to be a Quantum Refractor in the background of Cubit Foxtar's arena/boss room in Mega Man Zero 3. Another fact worth mentioning is that many enemies (almost exclusively the small flying enemies) bear a red eye that is extremely similar to the Reaverbots. If one takes a look at the Model W Core in ZX, it is interesting to note that it is covered, in various places, by the eyes similar to the Reaverbots in the Legends series. The Model W Core also has what looks like a stitch-like mouth, also related to that of the Reaverbots.
Interestingly enough, Purifer Units in the Japanese versions are called Irregular Hunters (Maverick Hunter). However, the fact that the Irregular Hunters in the DASH, formally (but not necessarily) the Zero series and the X games are the same thing is speculation for now. Also, the world of Terra is called Earth in original Japanese version. (This was carried from Mega Man V for the Game Boy.) Even more interesting, Elysium in the Japanese version of Mega Man Legends 2 (Rockman DASH 2) is actually called "Heaven"; A blueprint with the name "Project Heaven" supposedly exists in Mega Man ZX.
Have fun with that...I feel bad for knowing that much about Megaman...