Because it's the first console in a while to offer a competent alternative to PS/XB without great compromises
The 3DS had many great Nintendo exclusives but it looked like a toy, graphics were disappointing and lacked Nintendo's multiplayer factor.
The PSVita offered console-like experiences on the go, but lacked of any real killer app and was generally not much supported.
The WiiU had some great Nintendo exclusive but it didn't offer pretty much anything else, plus it was too expensive.
The Switch basically has all of the strenghts of those consoles and none of the downsides.







