Each mode has a time when it gets "good enough," and everything on top of that is gravy.
IMHO, for 2D, that was achieved with the NES generation. And for 3D, with the GameCube generation. (My son fired up Metroid Prime yesterday on the Wii, and it took me a while to realize it was a GC game, not a Wii game.)
But, yeah, Super Metroid is amazing. I only played it recently (~6 years ago), never the original, and I still enjoyed it thoroughly.
In this particular case note that the Wii hardware is, to a large degree, a straight repackaging of the GCN hardware with a bit more RAM and a higher clock speed. That the Wii is not an extreme graphical advance over its predecessor is to be expected. :)
I do agree with you in general, though. Which isn't to say that graphical advances aren't still perceptible (compare SNES-era sprites to any of the positively gorgeous sprites from Odin Sphere or Rayman Legends), but at some point you cross a threshold where graphics cease being cringe-worthy and start being merely dated. FFVII is a cringe-worthy example, whereas The Elder Scrolls: Oblivion remains breathtaking to behold (as long as you don't look anyone in the face, that is).
IMHO, for 2D, that was achieved with the NES generation. And for 3D, with the GameCube generation. (My son fired up Metroid Prime yesterday on the Wii, and it took me a while to realize it was a GC game, not a Wii game.)
But, yeah, Super Metroid is amazing. I only played it recently (~6 years ago), never the original, and I still enjoyed it thoroughly.