There's definitely an ideal number of buttons in there somewhere. I had great fun with my Commodore 64 and still consider it one of the best systems for playing games ever, despite games only using one button joysticks for the most part. Two buttons weren't quite enough in the 16-bit era. Six seems to be pretty ideal. I liked the layout of the SNES controller with four buttons plus two shoulder buttons though this wasn't necessarily the ideal layout for Street Fighter 2. These days I feel console controllers have too many buttons. More than 6 buttons and it just becomes a chore to use...