WOW.
Never played the NES huh? Go for Dragon Warrior!!!
Indeed, all four are just amazing. I'll throw in a few recommendations (I own an NES with almost 200 carts myself, the console is one of my favorites)
-Dragon Warrior I-IV
-Final Fantasy
-Crystalis
-Super Mario Bros. 1-3
-The Guardian Legend
-Life Force
-Gradius
-Faxanadu
-Double Dragon II
-The Mafat Conspiracy
-The Legend of Zelda/Zelda II: The Adventure of Link
-Mega Man 1-6
-Adventures of Lolo 1-3
-Kirby's Adventure
-Castlevania 1-3 (you might find the second to be a little odd or meh, I personally enjoyed it)
-Batman & Batman: Return of the Joker
-Blaster Master
-Journey to Silius
-1943
-Bobble Bobble
-Solomon's Key & Fire N' Ice
-DuckTales
-Gargoyle's Quest II
-Goonies II
-Bionic Commando
-Metroid
-Mike Tyson's Punch-Out!!
-Ninja Gaiden 1-3
-Kabuki Quantum Fighter
-Power Blade 1&2
-Solstice (hard as f*ck but an enjoyable experience)
-Teenage Mutant Ninja Turtles II and III
-Willow (Zelda-like RPG based off the movie, very well done IMO)
-Tetris (Tengen Tetris is better but there's nothing more 'classic' than Nintendo's)
-The Ultima games
If you are interested in collecting repro carts, which I'm not against myself as I have a few for the SNES (Tales of Phantasia and Seiken Densetsu 3), I'll throw a few names out for you:
-Sweet Home
-Ys I, II and III
-Dragon Slayer Jr. Romancia; if you like a good challenge
-Mother/Earthbound Zero
-Parodius
-Ufouria
-Moon Crystal
-Glory of Hercales II
-Holy Diver
-Esper Dream 1 and/or 2
All that should definitely get you started, I know there's a few I left out, it's a console that's good for discovering things on your own for the most part

I know that there's several that others could recommend too.