Heres a Nes Emulator for the Nintendo Switch:

UPDATE_3: NES ClasSwitch Alpha v0.0.3 Release

This update adds full speed gameplay and full screen scaling.

UPDATE_4: NES ClasSwitch Alpha v0.0.4 Release

This update adds support for several new mappers: (0, 1, 2, 4, 7) all games using these mappers should now run on the emulator.
If you want a list of compatible games google "nes big ass mapper list" and it should be the first page.(I can't post links yet) From there you can see what mapper each game uses.
Audio support is still in the works as well as save states.
Once these last things are implemented I will work on making the UI much better.

UPDATE_5: NES ClasSwitch Alpha v0.0.5 Release

This is a small update I thought I'd post for people wanting to play multiplayer.
This update adds joystick support for movement and multiple controller support for multiplayer.(NOTE: since there is no controller setup menu at this point its currently set up to use 2 full joy con controllers for 2 payers(i.e. 4 individual joy cons.) in future releases I will add a controller setup menu so you can configure it however you want... ex: 2 individual joy cons as 2 separate controllers.)

download https://gbatemp.net/threads/nes-emulator-port.504776/

via https://www.nintendomax.com/viewtopic.php?f=168&t=16603