But i disagree with that. Both Super Metroid and Metroid Prime belong to the same genre. Just because one is 2D and the other 3D doesn't mean the genre is different. And btw, Metroid was always a very hard title to put into a specific genre anyway. It's just Metroid.
OtherM was the one that actually changed genre. It became a simple action/shooter game.
2D and 3D games are approached fundamentally differently on, like, every level. I think unless you decouple game genres from mechanics, there's no way Super Metroid and Metroid Prime could be put in the same genre. Breaking things down to their most basic level - like, in terms of player control - Super Metroid has more in common with, like, Contra III (and Metroid Prime with Quake) than the two games have in common with each other, and that's really the most solid way to draw genre comparisons.
Also, yes, Other M is a different genre than Super Metroid and Metroid Prime, but not for the reason you state. (It's really just a matter of degrees, anyway - Other M still absolutely has classic Metroid secret-finding and exploration, just to a lesser degree and backloaded).
Metroid, at this point, isn't a series tied to a specific genre - it's really more about a general type of progression. Metroid games, primarily, are just about progressing through an open / interconnected world by collecting powerups that upgrade your traversal, and that's something you can do in many genres, including 2D platformers, FPS games, and 3D action games. (Although this is kind of tangential to the point of the thread. I think you could potentially make a great Metroid game out of a third-person shooter that follows the Metroid formula for world design and progression, but you could also just make a great third-person shooter bearing the Metroid license. Both would be equally valid Metroid games.)