Game Console Gamepad Controller - Dismantled for reference and curiosity
In the same way the console it was designed for revamped the failing electronic games market in the US, the NES Controller did much the same for game controller design.
While the controller brick wasn't anything new, Nintendo's use of the directional pad design created by Gunpei Yokoi for Nintendo's 'Game & Watch' LCD handheld games moved them away from traditional joystick controllers. The Intellivision controller did make use of a D-Pad style disc prior, but it's execution did little to endear the public to the idea.
The design was originally used on the Nintendo Famicom where the controllers were hardwired to the console as opposed to the proprietary seven pin connector version on the NES.
The NES controllers both have Start and Select buttons whereas on the Famicom only the primary or player 1 controller has these buttons. The second Famicom controller incorporates a microphone that's not replicated on the NES version. This means there are a select few games that certain actions could not be completed without this feature; eg. The Legend of Zelda.
Design-wise the controller is basic yet very functional with the main complaint being that prolonged gaming sessions would be more comfortable if the action buttons had been up higher rather than close to the bottom.