Wave bird sold millions, and was really the first commercially viable wireless controller. In an era of original "duke" controllers and IR ps2 remotes, it was a huge push. Just dig up some really reviews from when it first launched.
I know it was well received, but I want figures on how much it sold etc. Millions you say?
I would give it much more credit if it was included with the system to begin with, but it was an optional accessory on a relatively niche console.
It looks like the Wavebird was the first game controller to use 2.4 GHz wireless? Well, that IS a pretty big deal.
I think it's also fair to look at things other manufacturers have innovated that Nintendo has taken on board. Dual analogue sticks, home buttons, USB inputs, headphone/mic port on controller, hard drive, HDMI out, memory cards etc etc. They've definitely lead the charge in control innovation in particular, but I kind of feel like the others don't really get enough credit for their innovation that were subsequently adopted elsewhere.