Spanning the Bridge

For a series of video games, Mega Man is an ancient one. When Capcom first allowed a group of upstart programmers around Keiji Inafune to try and make a home console game, they never imagined it would eventually rise to become the biggest video game franchise, from sheer number of games in it. I've already detailed the beginnings. The classic series defined a lot of things that would be eternal mainstays, and laid the groundwork for what was to come. Simple run-and-gun gameplay, with two welcome additions introduced gradually to make it unique: the slide, which sped up gameplay considerably and also served as a tactical dodge move, and the charged shot, which made the basic weapon far better and also changed combat tactics to require more precision, less button-mashing. Basic game progression: Freely selectable stages with a boss at the end who'd yield his weapon for you to use, a weakness order to them, then a final gauntlet. It worked, and well at that, so Capcom decided to never ever change that. Instead, when the first Mega Man game for the Super Nintendo rolled around, Mega Man X expanded upon the existing concepts and singlehandedly made a series that was almost left behind by the changing times relevant again.
Two new concepts ported the gameplay into overdrive: The dash, which made everything quicker, smoother, leaner, more action; and the walljump, which opened up countless new level design opportunities as well as more tactical applications in high-octane bossfights than there ever were before. As the series progressed, especially those bossfights became the best parts, adrenaline-driven nonstop action fiestas.
One other thing the X games added was a bigger focus on story. While still hampered by Capcom's writer being incredibly awful at actually coming up with something that makes sense, there definitely was a very noticeable swell in scale and, for lack of a better word, epicness. Eventually, Inafune decided to let the series end on a climax of both, with a literal bang, and X5 was the most story-driven game yet. At the sime time, its story was also the most incomprehensible and bloated with stupidity so far, offering shoddy retcon-fueled backstories and explanations noone really had asked for.
To replace the X series, Inafune called upon a small company called Inticreates, created and staffed by ex-Capcom employees, who had so far been not very successful, but had expressed a steady interest in developing a new Mega Man game. They were given free reign to do so, with Inafune having the last word, though. He specifically requested to have the main character now be Zero, who had served more of a sidekick role in the X games. Many more changes for the storyline were made over development, some very late, also because Capcom decided the X series should continue despite having had a definite end...without telling Inafune until X6 was already well on its way to become one of the series' worst game. But that's a story for another day.
In 2002, Zero 1 came out to a very warm reception, warranting three sequels. It still was a somewhat rocky start...well, you'll see soon enough!