As Ninty announced, we will get three more NES games in the Switch Online lineup - Ninja's Gaiden, Adventures of Lolo and Wario's Woods. Ninja's Gaiden is definitely worth looking into the most, but they're all great games in their own regard.
If you like Dark Souls and if you like to die a lot (like.....really a lot), Ninja Gaiden is the game for you. If you've played it already, you know what you're pulling yourself into but, nonetheless, it will be one hell of a ride for any gamer. The other two games are surprising choices, but they definitely deserve a spot on this list.
You can get Switch Online for £17.99 if you don't have it already.