This game handles multiple playable characters better than any other Classic Megaman game in my opinion. The difference between Rock and Roll is big enough to where you feel like the choice is important and you'll have a preference but not so big that you'll go into some levels thinking you made the wrong choice or having one character be substantially easier/harder than the other. Outside of the character split I found the levels and boss designs to be not amazing or anything, but perfectly fine. It's a Megaman game so it's inherently fun regardless.
Definitely a good fangame, prefer it over quite a few official titles.

I have very complex feelings about this game, but I don't really feel like getting them all out right now. Might come back and elaborate later but for now I'll just write the following:

-Level design is generally good though sometimes it can be annoying (Area G + Area L)
-MMZ gameplay returns for the most part which is awesome though notably it feels like this game is less oriented on combat than those
-The map system is just stupid and the little amount of side-quests it offers is NOT worth the annoyance of going from area to area to start a level (even worse if you don't have a map handy)
-The biometal system is really cool in theory but in practice I find I tend to just use model ZX or model H
-The way you get higher biometal levels is really cool (having to avoid hitting certain areas of a boss) even if it can be annoying at times (stupid lion man)
-Hard mode is actually hard (still haven't been able to beat the final boss with it on, embarrassingly)
-Aesthetically great, maybe the best in the entire MM franchise
-The secret boss and optional biometal you get from it are cool asf

This game fixes my problems with the original Megaman for the most part with new stellar level designs and (less important but still) a better art direction. That'd make this good by itself but the developers had the absolute genius idea to make each and every Robot Master an unlockable playable character.
This decisions adds so much replay value it is actually incredible. On paper you wouldn't expect the game to change much just from changing the weapon (and admittedly for some characters like Fire Man it doesn't) but it can really flip the entire game on its head. Going through the stages again with a different moveset that you need to learn is just so nice, it really boosts this game up for me.

The soundtrack is good yeah, but it's a real shame that that's the only thing I see talked about when this game is mentioned.

Graphically, I think this game looks very good. There's not really much I can say on this topic but everything is clear, the pixel art is clean, and I never felt overwhelmed by the visuals.

The actual gameplay is exquisite, being easy to learn and hard to master. Comboing enemies together using your 'rang can be very satisfying, and rolling through levels in time trials is equally so. These inherently fun elements are amplified by wonderful level design, in both normal and hard mode. On the topic of hard mode, it turns what's normally a fairly average to easy game (except for the difficulty spike near the end) to a game genuinely deserving of being called "hard".

I don't think I can really explain how good the gameplay is because like I said, it's that category of simple with a lot of depth to it. I will say though, I'd recommend this game to anyone who's a fan of platformers.

I really don't get why this game is hated as much as it is.

The gameplay is good, I could see the argument that it's repetitive but I think the variety in enemies which necessitates changing strategy makes that a non issue. The difficulty is definitely low, but the only time that really bothered me was the end as even if it's easy, you still have to be engaged to win. The ending area in general is really a letdown with how pathetic the bosses are and the ending itself is bad too.

The story overall I thought was fine, the characters don't speak all too much which is a shame because I like the Sonic cast. I enjoyed having a range of dialogue options to use as Sonic even if some of them were wildly out of character. The actual narrative was pretty generic and mostly uninteresting, but it doesn't take up too much of your time here so didn't really bother me. I do think the idea of the Nocturnus Clan is cool but nothing is really done with it. Seeing Gizoids again was cool.

And even though this game's OST is deemed as godawful, I genuinely liked it. Sure, the instruments are very generic which gives it that "midi" feel but I don't think that's necessarily a bad thing, they work.

So I enjoyed it, it wasn't great or anything but it didn't have any glaring flaws while it had a few positives.