The perfect continuation of the series
Okay, first of all, almost everybody noticed that series that started on the NES often begin with a game considered as great, classic, etc... and then the company behind it decides to do a sequel, but changes too much things in it and eventually the game goes overlooked. Remember Zelda 2 where the game have a weird world map and all happen in side-view ? Remember Final Fantasy 2 where there is no levels ? Remember Castlevania 2 with it's unlinear gameplay and weird night-day system ? Remember Fire Emblem 2 where you can chose where you go on a weird world map before doing your missions ? Oh, and I did not mention Super Mario Brothers 2 (because it's actually a fake Mario game). (n.b. I didn't say the games mentioned above were bad, I just say they are considered weird by most people). Well, does Mega Man 2 try too much weird stuff from the original and end up being overlooked and considered not as fun as the original ? The answer is NO ! The only change from Mega Man 1 (except levels and bosses, of course) is that the game is much larger, have much better music, better graphics, added passwords, added a cool intro, gameplay glitches are fixed and the useless score is removed. The only "weird stuff" that was added is the selectable difficulty level, which I'll cover later when it'll be time.
Mega Man 2 is just the perfect sequel to Mega Man 1. Capcom just couldn't make the series go in a better way. The game is downright fun to play ! You have to defeat 8 cool elemental bosses in their respective elemental stages, take all their weapons and go defeat doctor Wily in it's fortress using your large choice of weapons at good use.
The graphics have changed a bit singe Mega Man 1. They look less sci-fi, and more... artistic. One thing I loved is the giant faces that pops up in Airman Stage, the animated lava in Heat Man and the infamous Dragon miniboss of doctor Wily's stage 1, to mention the most memorable scenes of the game.
The music is *amazing* ! Most song are based on techno beats and have cool solos in them. The boss music is sort of terrific, and add a lot to the overall fun when those bosses shows their nasty face ! And the music of the first two doctor Wily's stage is the BEST music I've ever heard on the system !!
They added a password feature, but I really don't need it to beat the game (at least in Normal Mode). I guess less experienced gamers will be happy to have it when discovering the game for the first time. Yes, the game is really not very hard, at least not until the last few stages. If you found the original Mega Man was hard, you'll found your bliss here (I personally think both are beatable if you have some skills in your fingers).
There is nothing terribly wrong with the game, just one major complaint : One particular boss in a Wily's fortress is impossible to beat without dying once. So, no matter how good you are at Mega Man 2, you just cannot beat the game without loosing a single live because of this. And if you reach that particular boss with no live left, no matter what will be your performance, you'll run out of mana without beating the boss and have to start the whole stage again. That kind of add strategy to the game, but I don't think this was a very good idea overall.
One other complain : There is two difficulty levels, and I think the "Normal Mode" makes the first 8 bosses way too easy (some bosses can be defeated in TWO HITS if you pick up the good weapons), but finishing the game in "Hard Mode" is almost impossible (or at least it is much more a challenge than finish Mega Man 1). Couldn't just they put one single difficulty level and made it well-balanced ?
Oh, both the American and European covers SUCKS ! However, I'm pretty sure the Japanese cover is much better, and actually feature Mega Man on it (instead of that ridiculous robot that miserably fail to represent the cool blue bomber we all know).
The sound effects in the PAL version of the game are a bit glitchy, but that is only in the PAL (i.e. European) version, not is the NTSC (i.e. American) version.
Last complaint : All weapons are cool and useful (like in the previous game), except one particular weapon, the Flash, which is totally useless. It just freezes enemies, but make you unable to do anything but move around until your mana is expired, and then you cannot use that weapon again (until you restore it's mana). It is useful only in Quickman stage if you want to stop the lasers, but come on, that is cheating. Avoiding those lasers isn't really that hard.
The Bottom Line
Mega Man 2 is an awesome game. If you like the Mega Man series, or if you just like platformers, I strongly recommend to play it. Download it for your NES emulator, and if you found it on a garage sale, buy it ! For collectors, I recommend importing the Japanese famicom version instead (called Rockman 2) because art for the western versions sucks.