After the Legacy Collections came to Switch I bought the first one and played through the games again. First thing I noticed... maybe I was imagining things but I swore there was noticeable input lag, even more so than there normally is on a monitor. Past that, another weird quirk: Any time you used the Switch's home menu and went back into the game, the audio became delayed as well. I... how do you even do this?
But I managed to adjust to the input lag (and again starting to think I was imagining it being worse than normal) and beat all six of the games again. I may get the second Legacy Collection later on but right now I'm a bit hesitant, although I do want 9 and 10 and more modern systems.
I'm too lazy to search for my original rankings so I'll just say that based on the NES games alone, I'd put them like this:
3>6>4>2>1/5
You know me, I don't like 2 very much. I think the robot master stages are fine, yoku blocks in Heat Man's stage and the instant-kill lasers in Quick Man's sage aside. I think the fortress stages are garbage, though. Unfun, with horrible bosses to boot. Really ruins the whole experience for me.
1 and 5... I honestly can't decide which is the worst of the two. 1 is dated, has horrible physics compared to 3 onwards (even 2's are an improvement but weren't quite there), has repetitive stage design elements, and its own fortress stages aren't the best. 5 is far more polished but it also has mostly forgettable music, stages that drag on way too long, not very good boss design, and horrible weapons. I had a hard time deciding which I liked less so I just put them together.
3 is flawed. I can understand not liking 3 based on these flaws. Even its Wily Fortress stages aren't the best, but more due to feeling incomplete than being outright bad. I still highly enjoy the robot master stages and even the Doc Robot remixes, and its soundtrack is godly.
6 is easy, sure, but easy doesn't automatically mean not fun. Wonderful graphics, aesthetics, soundtrack, the weapon variety isn't really the best, sure, but far and away better than 5's.
4... I find some slight annoyance at enemy placement and fortress checkpoints but there's very little wrong with this game, I feel.
4, 5, and 6 all have really bad plots though, but at least 6's you can laugh at how absurd it is.