A virtual console (VC) will not be available for those that buy the Nintendo Switch on March 3rd. This means only Switch games can be played on launch.
Nintendo released this statement: “Virtual Console games will not be available on Nintendo Switch at launch. We will share more information in the future“. Usually you could go to the eShop and download older Nintendo games.
It has been rumored that Gamecube games will be featured in VC for the Switch. We will have to wait and see since VC won’t be up and running this March anyway.
If you own a Wii U, VC games can be downloaded on the eShop featuring titles on the Wii, N64, SNES, NES and more. The Switch console itself will be out worldwide on March 3rd, 2017.