MM: I actually really like that one, I'd give it a B+
MM2: I though MM had boss rooms, just MM2 did away with the enemies in corridors before boss fights. Anyway, I always just use item 2 for Heat Man's stage. I hate those disappearing block puzzles. Best music and in my opinion easiest if you choose normal. I agree with your A.
MM3: I loved the addition of Protoman, and of course sliding; I've never liked using Rush to jump higher, but I do think he was a cool addition to replace the "items" in MM2. That being said, aside from the amazing title song, I didn't like the music as much, and that difficulty of which you speak was a bit too high for me; I can usually only beat Snake Man before I quit. However, it is beloved by many and I want to get further, which says something about a game, so until I've at least beaten more of it, I can't contend with your score. I like it, I just need to get better at it.
MM7: I LOVED this game when I was a kid, my only problem was that intro scene not being skippable if you forgot your password, but Bass and Treble were so cool, and that opening scene was awesome to me at the time. I actually got close to beating it later in life, though as a kid I think I was happy just replaying the Ice level. lol I found out you could get a certain Capcom song to play in Shade Man's stage when I watched the Game Grumps' Let's Play.
Street Fighter X Mega Man: I got up to the second "castle" stage; I need to download the version that lets you save, though. I won't spoil anything, but in my opinion, it's really creative and fun, and I love the soundtrack mixes.
I probably watched clementj642 Let's Play all of the others on Youtube at some point, but never played them myself, so can't comment. I'll have to find that MM7 fighting game now though, thanks for letting me know!
Guess what Mega Man game I remember playing the most from my childhood, though?
That's right. Tiger Electronics, baby.