Holy shit Jeremy this is amazing definitely worth the wait despite the glitches here and there its still really fun to play.
Theres a few things that could be improved tho.
Sonic doesn't exactly work on slopes
Luigi needs a few alt sprites other than his smb3 all-stars sprites thats a minor thing so I wouldn't really worry about that just yet. (small problem here if both mario and luigi are being played at the same time and they both have a fire flower they will look exactly the same if they are using smb.1 style sprites) (also on this topic sonic would be pretty cool with his sprites from mania and megman could use his sprites from mm7)
It would be cool if Mario and Luigi had their spin jump form mario world.
There are a few pretty low quality sound effects for example the win song for megaman.
So overall some pretty minor stuff if you wanted help ripping some sprites and or music im up for it so hit me up :P (preferably on discord cus i rarely look through my emails) im pretty sure i have a NSF fle of all the music from MM2 so i can get ya a high quality version of that using good old famitracker.
Discord: bigdaddy2#3186 (Yes you already have me added)