I will buy one when they make some games I want for it and add it to the collection. (GB, GB color, GBA, GBA SP, Nomad, NGPCx2)

I don't think anyone will ever make anything as good as the gameboy sp (handheld wise anyway). That is the perfect handheld I can actually fit it in a pocket even the back ones and sit on it. Also the battery lasts an unreal amount of time.

For the DS
this one looks interesting.