Apologies if you know all this stuff already; I just like talking about it:

NES has more genre creating games than any console in history. PlayStation 1 was a similarly seminal thing, but NES was when the deep magic was written. A lot of its games simply had no predecessors; they were invented from first principles.

The exact choice of titles will depend on your enjoyment level for games that are pretty unpolished from today’s POV, but many of them are good enough to still hold up even now, when one still image or sound effect from a modern game might have a bigger file size than a whole NES title.

History factor: Metal Gear, SMB1, Double Dragon, Metroid, Castlevania

History factor but also still fun: Contra, Legend of Zelda, SMB3

Still fun but also hard as balls: Ninja Gaiden

Wild card: Bionic Commando