So let's look at a single joycon. I always thought it was cool that the Wii controller, which innovated the "remote" style of motion controllers, could also be turned sideways and used in the same way as the traditional gamepad that Nintendo invented with the NES. Joycons are the same, but smaller, more ergonomic, containing an added analog stick, and with a third way of holding it: the "thumbs-up pose" used for ARMS (and the milking simulator). So the controllers already have 1 more way of playing than (I think) the next runner-up, but that's not even getting into the modularity!
You can slide the joycons into the grip, to emulate a more modern gamepad setup, or onto the sides of the screen like with every handheld since the GameBoy, or just hold them free like with the wiimote and nunchuk (but no wire this time!). Then there's the wrist strap, which is not only detachable this time but also doubles as a larger area for the shoulder buttons, plus the wheel and at least two different detachable ergonomic holsters on the market. And with the versatility of the rails there's any number of innovative things that could be clipped onto single joycons, the console itself, or the grip that we have yet to see (likely more useful than all of the sports accessories for the Wii…)
But on top of all that, the console itself can be played in your hands, on its kickstand, or in the dock. Even the dock has multiple uses: it charges, connects the console to the TV, and toasts sandwiches! And with each of the components detachable from one another it'll be easy to upgrade individual parts later on, when newer technology becomes available
TL;DR: The Switch is a swiss army knife among shivs. I can't even think of another piece of hardware so versatile and yet so elegant