Publisher: Capcom
Developer: Capcom
Size: 8 megs
No. of players: 1
After a seven year search, finally got it for: $99, complete(even had the Japanese registration card! More on that here)...and yes, it was worth *every* penny!
There is a God, and this game proves it. It's a compilation of Rockman/MegaMan 1-3 with updated graphics, sound and a bonus game called "Wily Tower". It plays like a dream, and looks even better...it's a shame it's so amazingly hard to come by...

What's it all about?
It's non-linear, lighthearted shooter. Playing a RockMan(MegaMan here in the states) you'll run along in the various levels shooting at other robots, and picking up energy(life) and weapon refills. More than just running from level to level, this series of games plays a bit to strategy as certain levels and bosses are much easier after you've acquired equipments and weapons from another stage. Basically, you pick what boss you'd like to go after first, you make your way through his area, destroy him and you then acquire his weapon(or a version there of). You can then use this weapon for the rest of the game, on other enemies and bosses...
Graphics - Gorgeous! Though MM1 received the biggest graphic update, MM2 and MM3 look damn good as well with their updated levels and enemies. The Wily Tower is all new, so there's nothing to really compare it to, though it looks fabulous as well and adds a lot of special effects that aren't in 1-3. The only real downside to it all is the slowdown that shows up during most boss fights. It's unreal, and there's reason for it...but it's there. Kinda disappointing, but you'll get over it...
Sound - Whips-fucking-Ass! All of the old school MM tunes have been redone with the Genesis in mind. I cannot even begin to describe the ultimate bliss of hearing WoodMan's level through the Genesis' more powerful sound chip. Along those lines, the levels in the Wily Tower have some kickin' new tunes that rock! Sound effects are great, again due to the Genesis' more powerful sound chip, sounds come off with the familiarity of their NES counterparts but with the added instruments, etc. of the Genesis' sound chip.
Control - Silky smooth. Mega controls as beautifully as he ever did on the NES, and that addition of using the Genesis' "A" button to bring up the Items menu is an improvement over the old "Select" method on the NES.
AI - It's MegaMan, and old school MegaMan at that so at times it can be really cheap. Hits that come out of nowhere to knock you off platforms and such are abundant throughout most levels. Oh, and the ElecMan Lightning Bolt trick from MM1 doesn't work anymore, so get ready to actually fight the bosses rather slapping them with one beam and bringing the items menu up and down until they are dead.
Replay value - Unlimited. With each game being a learning experience, trying to figure out which weapons and items work best on each level and boss is a lot of fun. Add in the Wily Tower(after the completion of all three games) and that fact that ALL weapons and items are available, though you can only take six or so with you, things can get very interesting with the combinations you come up with.
Tips for better gaming experiences:
If you're having some trouble making your way through the three games, take a look at the two FAQ's over at GameFAQ's.

Also, rather than bust your ass looking for an MD converter, just use the Game Genie to bypass the region lock this game has.

 Game Genie:
Region Bypass: V2AT-BMEJ + EAAT-BL1T + REBT-A6XL

My serious thanks go out to Trevor Wilson for creating this code, and his wonderful FAQ!!!

My rating: 95(out of 100) - An amazingly good update for the best three Megaman games in existence. 5 points had to be taken off due to the slowdown exhibited in some areas and most bosses though.

JD's frisky review: $99? $99!? You know how many cat toys he could have bought for me!? Though the collection is really good, the slowdown is unacceptable, making a lot of boss fights easier as a result and putting a serious hamper on the gameplay.

Click above for a larger view of this ultra-cool pic!
The wonderfully updated Rockman.
Rockman 2, WoodMan's stage.
Rockman 3, getting blasted with snake spit.
Oddly enough:
Another Rockman collection came out, in Japan, later on for the PSX. This collection included Rockman 1-6, WITHOUT enhanced graphics or sound. It REALLY is just the NES games, complete with NES sound and graphics. Ugh! For a list of all the changes that occurred during the conversion to the Mega Drive, check out The Mega Man HomePage's Rockman MegaWorld section.

Speaking of the soundtrack, click on any of the following for music from the Genesis version of the game: Rockman, Rockman 2(you're listing to this now), Rockman 3, Rockman: Wily Tower.
Mega Good :
Mega Man 2 was number 73 in EGM's "100 Best Games of All Time" list.(Note: This was the NES version)