Nintendo has updated the Nintendo Switch Online: Nintendo Entertainment System and Family Computer applications.
What is new for January 2019?
You’ll be able to play Zelda II: The Adventure of Link, Blaster Master.
And Joy Mech Fighter (Japan only) if you are a Nintendo Switch Online member.
Zelda II: The Adventure of Link originally came out in 1987 for the NES and is a sidescrolling rpg, with which the game in terms of gameplay was very different from The Legend of Zelda, which came out in 1986. Blaster Master came out in 1988.
While Joy Mech Fight is exclusive to Japan, people who have a Nintendo Switch Online subscription in another country can still access it. What you need to do is create a Japanese Nintendo Network ID and log into it on your Nintendo Switch.
When in the Japanese eShop, download its Famicom Nintendo Switch Online app to your system. Then, log into the Famicom Nintendo Switch Online app with the account that has an active Nintendo Switch Online subscription.