ShadowMan wrote:The Guide Books are some of my favourites as well - nice full colour guides with trivia, tips and really nice artwork. Capcom also released Strider, Dynasty War 2, Mighty Pang Collection and all 5 Capcom Generations Volumes in the same format which I am currently tracking down.
As far as finding the rest, search YAJ for カプコン レトロゲーム コレクション (Capcom Retro Game Collections) and カプコンゲームブックス (Capcom Game Books).
Ok, onto the game variants!
The first one will probably make you facepalm. Megaman for NES (US):
Both boxes indicate they are "REV-A," but the small box tabs and upper right hand corner of the manuals indicate the version. The right-hand box is NES-MN USA. The colors are richer for both its box and manual vs. that of the left-hand box, NES-MN USA-1. The back of the boxes are identical. NES-MN USA is usually identified by a big round sticker on the bottom front of the box. This copy got away without one, somehow
Next up we have some PAL games! Megaman 2 (PAL):
There was an A version and B version of this particular game. First off, you will see different Capcom logos on each version. If you inspect the front lower portion of the boxes, you may notice a humorous discrepancy in the fine print, below the Nintendo logo

The majority of the text is the same and the major difference between the two is merely in the formatting. Also note that version A has a date of 1990, while version B claims 1988 (kinda backward, eh?).
Megaman 3 (PAL, Mattel logo version):
This is the only version of Megaman 3 PAL that I own, so I cannot speak in detail on the differences between it and your copy. I just noticed that your's didn't say anything about Mattel!
Megaman X (US, Majesco version):
I don't have photos of this for you, as I have since sold mine. As far as I recall, the front cover was basically the same, but the back has text that denotes it as being released by Majesco and manufactured in Mexico. Also, the manual is black & white, rather than the nice full color original release. They are not worth nearly as much as the original release. I ebayed my sealed copy last year and it only went for like $90.
Megaman X6 (PAL, German version):
The copy on the right has a different logo on the cover, above the Playstation hologram. The back, rather than the 3 language version, is only in German and features different art. The manual is also only in German. Although these are the only PAL X6 releases I'm aware of, some of the copies, like you have, have an Australian rating system sticker placed above the Playstation hologram:
Tiger Electronics Megaman 2 (French version):
Not much to be said here. It's French! Wee, wee!
Bandai Rockman X2 pocket game:
Bandai put out a small pocket calculator, organizer, game for Rockman X2 previous to the X3 Design Master unit you already have. I need to pick up a new battery for mine so I can remember what the game portion is like, but I don't think it's any more complex than the Tiger style games with fixed graphics.
Arcade:
Oh, boy. This part of your collection will give you a headache, for certain! Why? Because arcade operators are notorious for throwing away "worthless" boxes, papers, stickers, etc.

Putting together a complete kit is a nightmare unless you are so blessed as to find a kit that was shelved and never taken apart.
Playchoice 10 Megaman 3:
I got a pretty smokin' deal on this kit years ago. I don't know what it would be worth today, but I can guarantee it would be a fair amount more than what I paid!
Megaman 2: The Power Fighters:
I picked this kit up from a Capcom distro. maybe 7 years ago? I Played it and enjoyed it, but just couldn't justify having that kinda money (and space! The thing is huge!) wrapped up in one item. I've since sold it to a swell chap across the pond.
Rockman: The Power Battle:
Holy cow is it hard to find original art and manuals for these! I managed to land an untouched manual + artset for this! Unfortunately, CPS1 boxes are rare as hens teeth, so I'll just have to wait it out on that part.
Rockman 2 The Power Fighters:
This is almost a complete kit. Unfortunatly the art has seen better days (though it is original). The box is from an X-Men vs Street Fighter kit, but it is true to what this game would have shipped in.
Rockman: The Power Battle CPS2 RENTAL version:
That's right, Capcom did a limited run of the first Rockman arcade game on CPS2 hardware! The collector I sold my Megaman 2 arcade kit to owns the one in the photo. Beware of shady sellers selling bootleg "prototype" copies of this game on non Rental carts (i.e. anything other than Yellow).
Well, all that should keep you busy for at least a few more years of hunting

I've got some other fun merch. to show off, but I'm gonna call it quits for tonight!
Here's a sneek peek of a Rockman case I'm slowly organizing:
Oh, and one last thing, here's
a little article I threw together about a game from the original Rockman series that is sure to keep you from sleeping tonight

-ud