Mega Man 2 makes many improvements over its predecessor, and establishes the majority of motifs that would define the original Mega Man series. The game is much more polished, but what really makes it shine is how thoughtfully it is set up. Unlike every other Mega Man game, Mega Man 2 doesn’t feature anything approximating a single order to beat the bosses in. This is the most free-form the series would ever be.
MM2’s greatest strength can be a weakness at times, though. Metal Man’s weapon in particular is insanely overpowered, in terms of its general utility, energy efficiency, and even how many bosses it’s useful against. The manual suggests beginners fight Metal Man first because his weapon is the most useful, and that’s an understatement. While Mega Man 2 does offer some other interesting weapons, you’re usually better off using the Metal Blade than anything else.
The focus on one overpowered weapon aside, the structure of Mega Man 2 is very interesting and leads to a lot of replayability. Some bosses have several weaknesses, and there are even easter eggs like Metal Man being incredibly vulnerable to his own weapon in the rematch. There are a few lame weapons, and MM2 establishes the series tradition of requiring the least useful weapon to fight the final boss with. Even those weapons have their uses if you look for them, though.
One place MM2 really shines is in its level design. These levels and their fantastic music are very memorable, between the huge Air Tikis in Air Man’s stage to the multi-tiered ice hallways of Flash Man’s stage and the force beams of Quick Man’s stage. Of course, memories of those force beams are unlikely to be especially positive. This is a difficult game, and even though it has two difficulty levels, the easier of them doesn’t do anything to make environmental challenges like these any easier. (Fortunately Quick Man’s design is so cool that it’s easy to forgive him for having such an unfair stage.)
There isn’t much to say about Mega Man 2 except that it’s a lovingly-crafted and perfected follow-up to the original Mega Man. The difficulty spikes are mostly smoothed over, and the game is filled with set pieces that are cool now and were positively mind-boggling in the NES era. The dragon boss in particular comes to mind. This is a classic that any Mega Man fan owes it to themselves to play. These days, there are so many version available that that shouldn’t pose any kind of problem.