SMB3 and the NES Mario games were ported over to SNES, numerous SNES games were ported over to GBA, some N64 titles were on DS, Wii games weren't retro and were on eShop for Wii U with some titles like DKCR and XBC being on the 3DS as well. This is something that has been done long before Wii U even when the platforms were successful.
N64 titles on DS were retro, SNES games on GBA were retro, Wii games on Wii U eShop weren't even ports, just ripped ISOs. The only example that applies is the Super Mario games ported to SNES but they only ported Mario, not the myriad of other titles on NES. Never before Nintendo ported so many titles from a console so soon after release.