Not too long ago I stumbled upon something about a fan game being made called Mega Maker. Essentially it would be similar to Super Mario Maker except for Mega Man. I kind of forgot about it until today when I noticed it had been released for download. I checked it out and I've got to say it's pretty nice. One of my only nitpicks so far is that when playing stages the game moves at a little over half the speed it normally should which can be a bit annoying, but so far it looks pretty good.
I checked out the stage editor and it gives a pretty extensive tutorial for how to create a level. You can a lot of assets from Mega Man 1-6 including enemies, backgrounds, music, and robot masters, as well as give Mega Man a custom weapon and item loadout for your stages. My other nitpick is that there's not much from each game you can use in terms of enemies, weapons and robot masters, plus there's only three weapons from each game, two robot masters from each game, and three utilities (Magnet Beam, Rush Jet, and Rush Coil). I'm kind of surprised they didn't at least put every weapon and robot master in to give a much wider range of possibilities, but hopefully that'll be updated sometime down the line. For now though it's not bad and I'll probably check out some more levels in the near future.