Yea only the directional pad and FIRE button (`B` I think) will work.
Games which use the CD32 contollers` Shoulder Pads, green, yellow, blue, and START buttons will not work with a Sega controller.
Get a CD32 Competition Pro controller - it`s best of both.
It's completely compatible with the C= CD32 joypad.
"Some good things said about it are that it's shaped like a Megadrive
joypad, the diagonals are easier to get to, it feels less delicate, it
has turbo and auto fires, and it has a slow motion button.
Some bad things said about it are that it's shaped like a Megadrive
joypad and the diagonals are more difficult to get to.
Obviously a bit subjective."