SNES pad you just need to lop off the SNES end and replace it with a NES end, as they use the same protocol.
The others will require either a microcontroller to translate their output to SNES/NES signals, or to have their original circuitry removed and replaced with the logic of a SNES pad.
dont need to sacrifice a NES controller to do so. Get some Shift regulators from Digi Key. Part number 296-2040-5-ND. Use it just like the IC in the regular controllers. (thx to Ben for the info)
The wood master
"I was under the impression Mac owners don't actually USE their machines, they just parade them around trying to evangelize the masses."