This is the first MM game where the developers weren’t rushed and that shows in two ways. First, there is a noticeable step up in the graphics. More details are added, backgrounds are rarely ever blank, and there’s little nice touches like Skull Man’s stage turning to sunset at the end. Second, and most crucially, the late game no longer sucks. In fact, it’s great. The Cossack and Wily Stages are just as good as the RM stages, and the fortress boss fights, while not as consistently good as the RM boss fights, are good and interesting because the bosses aren’t restrained to having to be, at least in size, Mega Man’s equal. The fortress bosses are able to take different forms.
Also, MM4 introduces charged shots. The approach to enemies doesn’t really change though. You can plow through this with buster shots the same way you could the previous games. I think this is a really good decision. Charged shots are optional, meaning they really only exist to make certain sections easier if you want.
In terms of quality, I say this game is just barely edged out by MM2. While the late game is obviously much better than MM2’s there’s enough spots in MM4 where the quality drops just enough to match it. Particularly, this game has weak midbosses. Ring Man’s stage, for example, has you fight two different midbosses twice, and both of them are not fun but take forever. The midbosses are too simple of fights, where only one or two things are going on, that they’re only able to be easy or annoying, and they lengthen these fights by only allowing a tight window for you to damage them.
But shoutout to Bright Man’s stage, such a good fucking level