Only their portables, though. The SNES had 4 plus two shoulder buttons in 1990, 10 years before the GBA. Honestly, I always felt like that was a missed opportunity for Nintendo, since the GBA was basically powerful enough to run SNES games, but lacked the buttons (and the screen was smaller). Made it impossible for it to be a port machine for all those great SNES games...
iirc in a recent episode [0] of The Talkshow, John Gruber and the people from Panic are discussing the button layout on the Nintendo Switch. They were wondering why the Switch has so many buttons and whether it was a pragmatic choice by Nintendo to make porting games from other platforms easier.
Made me wonder whether we're observing some variation of Hotelling's Law [1] in controller design.
PS: the episode mostly is about Panic's upcoming handheld game console Play Date [2] which also has two primary buttons (and a crank!).
The Switch has the standard number of buttons for a home console: four face, a D-Pad, two clickable sticks, Select and Start or their equivalents, and two shoulder triggers per side. Much of the escalation in number of buttons was done by Nintendo itself: the SNES was the first to have four face buttons and two shoulder buttons (Sony would follow up by adding two more shoulder buttons), and the N64 was the first console to feature both an analog stick and a d-pad (Sony would follow up by adding another stick). The current standard is right in the happy medium: enough buttons to enable a variety of actions beyond, say, "attack" and "jump", but not enough to overwhelm and confuse the player in the heat of play. Plus, the Switch controller can be broken into two, each allowing SNES levels of control for impromptu multiplayer play. So if it seems like there are too many buttons at times, it's because of games that deliberately use fewer buttons to take advantage of different play modes with the Joy-Con.