Final Fantasy 6 is a beautiful 2D game. It does not need a remake; it is pretty much perfect the way it is (although removing the mode 7 sections would be an improvement). Remaking it in 3D would be blasphemy.
Final Fantasy 7 is one of the ugliest games I have ever seen, and not just because of the hardware limitations. It stands out as particularly ugly even among the general ugliness of the original Playstation games. If ever a games needed to be remade, this is it. It already received a few remakes, but the more the merrier.