I think it is a bit more complicated than that. I think the issue may come down to consoles and communities more than sales.
I think it is nearly impossible to bring much over from the DS and Wii on a small budget as the controls will make it much harder to port. The DS’s two screens also make things difficult. The 3DS will also lack 3D. Unless they want to invest heavily, the past few consoles are an impossibility. The Wii U got lucky as most games do not utilize the gamepad.
As for GaneCube, I think Nintendo is just steering clear of the fanbase. Releasing Paper Mario The Thousand Year Door would be a risky move in the current climate. Melee is also contentious because, well, it is Melee, you know the reason Nintendo wants to forget it. A Sunshine release may clash with the rumored Mario 35th collection if it is real. Who knows what will happen with Wind Waker and Twilight Princess, as they can easily be brought back from Wii U. If those titles are off the table, then they likely see no reason to bring back others. Chibi-Robo is always going to get death. Mario Party will fight with current Mario Party, and so will Mario Sports. F-Zero is niche. Pikmin is in a weird middle ground that probably is not worth investing in. Animal Crossing is sort of dividing at the moment like FE and Paper Mario did, so? The Radiant games were poor sells and bashed by critics.
The only big ones are Metroid, which has been rumored for a Trilogy remake, and Kirby Air Ride. Neither were poor sells, have bad fanbases, will divide communities, or have possible remakes. The problem is, why not just remake them then?