Metroid 2 needs a remake because there is no Virtual Handheld, and thus no distribution of the game from Nintendo. Nothing of the modern generation can play Metroid 2, and like hell Nintendo'd allow themselves to just slap it down as-is on DSiWare. Though, if a Virtual Handheld does come to, a true-blue (and orange, and red, and yellow...) Metroid II DX would be the Zebes' knees.
Metroid 2 was my first Metroid game and I loved it! It deserves a remake. I think a 2.5d game would be fantastic. Also, I would love Retro Studios to make it as well. Their level design is unmatched and I believe that they could possibly make the most stunning 2d Metroid ever created using modern development techniques with 2.5d and 3d modeled environments(2d plain of course).