Megaman (Classic) is followed by Megaman X and later on Megaman Zero with a hundred year span between each saga. Megaman Legends and Megaman Battle Network both take place in in two separate universes.
If you want a plot review of the X and Zero sagas, just tell me. I love doing this stuff.
Actually, Legends takes place in the same one as Classic, X, and Zero, but waaaaaaaaaaaaaaaaaaaaaaaaaaaaay after all of them. It doesn’t matter; don’t bother trying to get the story, RC. It’s not worth the trouble, cos you find out the story isn’t all that amazing anyways. Just play the games, and be fascinated with that. 
Story has never been the strong point of the series.
I think MMBN is supposed to take place before the original MM series too.
MMBN Can’t take place before Classics since Light is already dead in it. And I heard about the rumor about Legends being part of the storyline but it just… well, it doesn’t “feel” right.
Told y’all the story was overly convoluted.
I literally haven’t paid attention to Mega Man since X4. Well, except for dling the first two MMBN roms (and barely playing the 2nd). The lack of contiunation of the original series, you know, THE IMPORTANT ONE, saddened me. 
If you are lucky enough to find it, get the Megaman Anneversary Collection for PS2 (or Gamecube if you so desire). That contains megaman classic 1-8 and some other ones that are unlockable, like the two Megaman arcade fighting games.
Following that, there will be a Megaman X collection coming out soon that will have all the 2D X games X1-X6 and some games that havent been released in america like the megaman racing game.
That should satisfy the thirst.
Megaman Anniversary is out on Xbox now, as well.
As has been said, Capcom has convoluted the story so they could keep making the games. Take it from me, the best means to preserve your sanity is to just go from the normal MM games, then to MMX, and cut off to MMZero at X5, pretend X6 and up didn’t happen. I personally am disregarding all the others as far as story is concerned.
erm Plot holes? X?
Yeah. This is why X6 was created (Contains X5 Spoilers) …
Capcom accountant: AAAAA!!! AAAA!!! AAAAA!!!
Director of MegaMan X5: What’re you screaming abut?
Accountant: AAAA!!! YOU KILLED OFF ZERO!!! AAAA!!! DO YOU KNOW HOW MUCH MONEY WE WERE MAKING OFF HIS EXISTENCE!?!?
Director: Well, yeah, but it was drama points. We’d make more money cuz of the tragedy, ‘n’ stuff …
Accountant: calms down … I guess you’re right … but what are we going to do for the se–
Director: I also made Sigma’s death a little bit more permanent, too …
Accountant: WHAT!? Why!?
Director: Well, I figured it was a good place to end the series …
Director: END THE SERIES!?!? AAAAA!!!
One of the greatest tragedies in the history of gaming was when they tried to add plot to the Megaman games. Don’t get me wrong, I love all those games still. But seriously, what the HELL was going on in X6?! And at the end, I thought Zero put himself in suspended animation for 102 years, or something! So WHY THE FUCK IS HE IN X7?! And don’t get me started on Megaman Zero.
I’d like to get you started on MMZero, I thought the story and game play are top notch for what it is. A gba platformer. So please, tell us your opinion.
Actually, I think X7-on-up takes place between X4 and X5. Or possibly an alternate universe. I dunno, really.
Regardless of story, Megaman games are really good. I love 'em! :kissy:
There is so much variation… we’ve got Fireman, Heatman, Flameman, Napalm man, er… um…
Silence
Or maybe that scene with Zero doesn’t take place inmediately after X6.
Can’t forget FLAMING COCK…I mean, Burn Rooster. >_>
I think I’m going to pick up that anniversary collection. Does anyone know if that Megaman & Bass game is included or not?
Plot of the megaman games: some guys make some robots and they fight each other and then OH NO EVIL ENERGY AND ROBOT SOULS AND ROBOT GHOST VIRUSES AHHHHHHHH
No, sorry. It’s got MM 1 - 8, plus the two Mega Man Power Battle games.