There’s been various Mega Man series, and as mentioned previously, there are connections, but there has been no real effort to make a serious continuity. Actually, there was one attempt, but it got messed up due to reasons that aren’t exactly common to video games (Marvel and DC comics come to mind actually):

Mega Man:
First is the original Mega Man series, which started for the NES, in 1987. Factoid #1: part 3 (my personal favorite btw, though 2, which is everyone’s elses, is a close second), in 1990 was the first to solicit ideas for bosses from fans. This continued on for the rest of this particular series, at least for its NES run (afterwards, a new Mega Man game came out a year), which last six games.

Then a few years part 7 showed up on the SNES, in 1995. By this time, Mega Man X had been established, so 7, being part of the “past” adopted a slightly more cartoonier and light-hearted esthetic, at least compared with the more serious and grittier X series.

A few years later still was part 8, in 1997, for the PSOne and Saturn. It was more or less the same thing, just far more prettier. Each games was more or less the same: Dr. Wily creates a bunch of bad robots which Mega Man has to destroy. Along the way, a few notable supporting characters are introduced, including Proto Man, in part 3, who pops up (sorta) in the other series.

The last of the “classic” line is Mega Man & Bass, in which Mega Man shares the spotlight with Bass, another supporting character (introduced in part 7) that’s sorta like Mega Man, but a bit more rougish. Again, this game was one of the very last games for the Super Famicom (what the SNES was originally called in Japan) in 1998, which is well into the N64 era. And its often confused as Mega Man 9, because that’s what it was called in development, or so some say. There has been no further old school Mega Man games since.

Also of note is a few Game Boy games that came out, which featured bosses from the original NES games, and a pair of arcade titles that features just boss battles, sorta like Street Fighter, which again just used bosses from the NES games. Plus there’s been a Mario Party-esque video board game, a Mega Man themed soccer game, a cart racing game, and an interactive cartoon title, all of which has never come to these shores (though the racing one popped up as a bonus in a recent compilation).

Mega Man X:
The second series is Mega Man X, which again debut in 1993. Unlike the original series, it was a bit darker, and the backstory as a whole was far more developed.

In a nutshell, a robot who may or may not be the original Mega Man was sealed away (due to fears by his creator that he may “go nuts”) and is later discovered in the future. He is then used as a basis for all robots from that point on, but some go nuts, and its up to Mega Man, who is called X, plus a partner, known as Zero, to stop the evil robots. Again, there’s an evil mastermind behind it all, like Dr. Wily, but not as cartoonish, plus I believe it changes at least once as the series progresses. Though the whole defeating a bunch of bosses and acquiring their abilities formula is retained.

Mega Man X2 and X3 came out for the SNES, X4 came out in 1997 was on both PSOne and Saturn, and X5 and X6 followed years later and on the PSOne only. X4 btw is generally considered the best in the whole X series, and is my third personal fave Mega Man game.

Factoid #2: the X series was supposed to end with X5, in which it is revealed that Zero is actually the creation of Dr Wily (I believe this also alluded to in X4… my memory is a bit foggy), and I even think he was based on Proto Man. His death is also supposed to set up the events in Mega Man Zero (more on that in a sec). But Capcom decided to be greedy and do a X6, which was less than stellar.

X7 came out in 2003 and is generally considered one of the worst Mega Man games to date (it tried to incorporate 3D elements, and bombed big time). Plus it introduced an new supporting, playable character named Axel. X8 came out last year and its a bit better. Also there’s been a RPG set in the X universe.

Mega Man Zero:
The third series to follow the same canon takes place approximately 100 years in the future in which this time Zero is uncovered by scientists at the time. Now the whole setting is dystopian and ultra hardcore sci-fi, plus religious overtones: X had managed to conquer all evil in the past and began running things, but went nuts (fulfilling the legacy that was somewhat implied by the plot of Mega Man X), so Zero must help a band of outlaws to overthrow the regime. Its the same formula as before more or less, but Cyber Elves have been added to the mix; creatures that grant Zero special abilities.

Thus far the series has been on the GBA only, with the first game coming out in 2002, and each subsequent sequel coming out a year afterwards. There’s been four thus far. It should also be noted that they are tough as nails.

Mega Man Legends:
Legends was the first attempt at a purely three dimensional Mega Man game for the PSOne back in 1998 (X7 has 3D elements, but its still at its core a 2D game). Its far lighter in spirit when compared to the X series, with an emphasis on pure exploration. There’s only been on sequel (plus a spin off game that has no Mega Man at all, and both are on the same console), plus it has no real direct connection to the other and later series, though some claim that there are subtle references in the Zero games (which I think are just the game creators having a little fun).

Mega Man Battle Network:
The first Mega Man series for the GBA, which debut in 2001. It has absolutely no connection to the other series whatsoever. The game centers on a society in which everyone has a friend/companion that resides on the information super highway, and the central character is a kid who’s cyber counterpart is Mega Man. The game consists of him jacking into the net and fighting computer viruses, and the bosses borrow names from the original series, almost in a wink-wink, in-joke kind of fashion. Instead of side-scrolling action, its more of a strategy RPG, and there’s been multiple sequels for the GBA (often in multiple flavors, a la Pokemon), and enhanced ports for the DS. Plus there was a more action based game for the GameCube, that harkens back to its side-scrolling roots, with strategic elements thrown in (rather awkwardly, if you ask me).

I haven’t heard of any more in the Battle Network series, though I’m not certain if it came to an end or anything.

Mega Man ZX:
The newest Mega Man series, coming soon for the DS. Not must is known right now, but it looks to perhaps pick up where Zero left off, but later on in the (further) future. It supposed to star two teenagers that harness “live metal” to transform into beings that look like X and Zero.

So yeah, to sum it up…

- The original Mega Man series is pretty much over with.
- Mega Man X, which took over for the original series, continues on…
- Meanwhile the events that happened afterwards, Mega Man Zero, has also ceased to be.
- And Mega Man ZX will perhaps continue to saga…
- Meanwhile, Mega Man Battle Network and Mega Man Legends, both of which have no bearing whatsoever (or so it may seem) on the continuity, have both seen their final games (maybe).

Christ, I was not planning on writing that much. I hope that answers something.