i love PS1/2/3 pads, both d-pad and analogue. I would recommend a PS1/2 USB adaptor for anyone using emulation, and a PS-CD32 Adaptor to anyone using original hardware!
On my A1200 though, my favourite is actual a Polish 3rd party PSX pad. The D-Pad on that is better even than the CD32 Competition Pro. (of which i am also a fan)
The Mastersystem pad is ok, but i dont really like anything that has raised points to stick your thumb into (the C= CD32 pads biggest and most painful flaw)
I quite like the original Sega Megadrive pads on the rare occasions i get to use them.