The NES, SNES, N64 and Genesis controllers work fine. I have not had a chance to try out the zapper though. I had to replace the N64 and Genesis controllers because they were broken. The replacements work fine, but they close to 20-years-old.
Once I get the games going, you can not tell a difference except for the console itself. I recommend this adapter for everyone. You can find it on ebay and it really gives n authnetic feel to playing VC titles. Unlike the classic controller and gamecube controller.