The TurboGrafx and 3DO had six-button controllers, but they were both created for the same reason as the Genesis six-button pad: for Street Fighter II. So it's probably more appropriate to credit Capcom for that. The SNES, of course, already had a six-button controller, though it did get some third-party controllers with six face buttons (including Capcom's Pad Soldier), again for SF2. There also the Microsoft Sidewinder, I guess. The four-button cross layout of the SNES controller has been more influential, of course, and examples for it are much less obscure, such as the PlayStation, the Xbox, most PC controllers, pretty much every retro handheld (and the Steam Deck), and even the Dreamcast.