If you enjoyed SFxMM, you may also want to try Mega Man Unlimited Unlimited and Mega Man: Rock Force. Both are also very solid Mega Man fangame titles.
In terms of fan games there also exists some good ones as well in the following:
In case you wanna know what the game in the first image is, it's called "Mega man rock force"
http://megamanrockforce.com/rockforcemain.html
go check it out, quite the banging platformer
Not ROM hacks, but Megaman Unlimited is easily my favorite Megaman fangame, really high quality, captures the feel of classic Megaman really well, and Megaman Rock Force is pretty good as well, if a little unpolished in some regards. If it's just ROM hacks you're looking for, it's worth checking out qzecwx's Youtube channel, he has playthroughs of lots of really neat Megaman hacks of all sorts, so there's lots of selection.