I'll leave out Megaman & Bass, seeing as I kind of want to give it one final shot at some point, preferably with the Super Famicom version, but at this point in time if I were to rank it, I'd put it at #10, which would make this list's #10 #11. But anyway, here we go:
10. Megaman 8 - This game is so much nope. Levels too long, voice acting super atrocious (Dr. Light's great for entertainment but the rest are just bad), music is forgettable and not really fitting to a Megaman game, and the lack of E-tanks for some godforsaken reason makes this game even more of a drag than it already was.
9. Megaman 2 - Far and away more bearable than 8, there's really a larger gap between my enjoyment of these two games than their list placement would say. But all the same, I find Megaman 2 somewhat fun with great music, but lacking in balance and the Wily stages are terrible. Especially Boobeam Trap.
8. Megaman 5 - "Bland" is the name of the game here. Levels go on a bit too long, most of the themes are forgettable, most of the themes are forgettable— well the first time I meant level themes and the second time I meant music. There's great music in here, to be sure, but a lot of it is not very good. Couple weapons suck, but on the whole it feels more complete than Megaman 2 and there's nothing I really dread about replaying this game compared to 2.
7. Megaman - Surprisingly I actually enjoy this game, pointless score system and slippery physics inside. Despite some copy/paste in some levels, everything just feels well-built. I hate that they require you to find the Magnet Beam or else you're stuck in Wily's Castle, but I love the weapon enough that I don't mind. There's some annoying factors, but there's always some workaround to them. Also the music is pretty good.
6. Megaman 7 - Honestly the 8-bit demake would be higher on the list, but in its original form it's not bad. Good even. Level design is fun, music is good, I like the addition of a shop... I admit the backtracking for parts is a little annoying, but it does add a bit more depth to the levels, most of which have multiple pathways, which is always a plus in my book.
5. Megaman 9 - This game has an outstanding soundtrack and tough but mostly fair gameplay. There's a couple of sections where I think the required jump precision is too much (here's looking at you, Jewel Man stage), but on the whole it's a super solid game with fun bosses and useful weapons. The final Wily stage is a pain in my ass though.
4. Megaman 4 - Highly underrated classic, in my opinion. Everything feels solid and smooth here, with the exception of maybe too few checkpoints later on in the game. It was probably the only game with a half-decent in-game story as well, not that I play Megaman for the story.
3. Megaman 6 - Same as above, highly underrated classic. Fantastic music, solid and unique level design, and the Rush adapters are quite fun to play with. It could have been the perfect end to the series if it wanted to be, especially with that badass final boss music. Even if the boss itself was easy, I guess.
2. Megaman 3 - I'll be the first to say that Megaman 3 has some problems. I'll also be the first to say that I don't care, because this game's full of pure entertainment to me. One of the best soundtracks, if not the best, in the series; fun and useful weapons; unique Robot Master design with fun stages... I even like the Doc Robot stages, though the bosses themselves can be kind of a pain. The final boss is laughable, but honestly, I've given up on final bosses in this series being challenging.
1. Megaman 10 - There's nothing but gold in this title for me. For one, its soundtrack is absolutely glorious. For another, the level design is overall solid and never feels too cheap, except in Nitro Man's stage, that stage is a pain. The Robot Masters are all fun and usually require a strategy other than just "wail on them directly with their weakness," and the weapons themselves are fun to play around with. It's a challenging game, a good challenge, and I wouldn't have Megaman any other way.
