The original Metroid higher than Zero Mission? I'm really curious about the reasonment, I think Zero Mission it's an outstangind remake, but I would love tho hear (or rather read) another opinion on the matter

They're both neck and neck but for different reasons.
I quite like the original Metroid after going through it, I think its pacing is stellar and the freedom it gives you makes it very unique among the rest, it has some glaring issues but I think what it does well far outweighs them and the fact that it's so unique makes me think highly of it.
I recognize that Zero Mission is really good but I don't think it quite captures what makes the original game so fun, and that's fine really, but for me if I wanna play a game where I explore Zebes with Super Metroid's control scheme... well I'd just play Super Metroid wouldn't I? A game which also has the benefit of not being incredibly obnoxious to 100%.
I'll say though the first four on the list are pretty interchangeable really and the most I can fault any of them for are tiny nitpicks which don't actually impact the experience much.

Oh I totally see your point, personally I belive that Zero Mission enhaces a lot of Metroid's positive qualities and eliminates some of the shorcomings, plus the ambience, changes and surprises it delovers are some of the most thoughtful I've seen in a remake, but I understant what you are saying and honestly, yeah, most Metroid games are so good they are practically much on par with each other.