The quality of game pads for the Genesis platform run the range from poor to great. I'd avoid pads made by High Frequency for example. I picked up a few metal cased arcade quality joysticks for Genesis from the game recycling stores a few years ago for a song. Very durable.
I have not researched this in depth, but, I've seen evidence that the Amiga and Genesis ports are not identical. Prior to the CD32, there was one fire button commonly used on Amiga. The Genesis has the same connector (9 pin limit) and they found a way to multiplex the 3 or 6 fire buttons used on their pads into the same connector. There is a chip in their pads for this purpose as well as tunable rapid fire, etc.
IIRC, there are two wires to swap and two resistors to add in the controller. After this mod, the game pad chip gets 5 volts and more buttons work. Then you have to find Amiga games that use these multiple buttons.
If you are interested in experimenting (try it with a machine with socketed CIA chips), I found this info in the docs that came with ADOOM on Aminet.
Good Luck!
