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.