Three versions of LttP...SNES, GBA, Wii.
Four versions of OoT...N64, Wii, the two GCN bonus discs.
Two DKC2...SNES and Wii.
I could go on, but eh.
Really, it's a matter of convience. It was easier to grab the GBA version of LttP rather than dig out my SNES every time I wanted to play, and it's easier to grab my classic controller and boot up my Wii than stare down at the GBA (Or rather, DS) screen.