Mario RPG is really entertaining for about half the game, then it's just more of the same.
Ocarina of Time looks terrible by today's standards and plays very slowly and clunkily (just made up that adverb).
Get Kirby's Dream Course. It's golf with an inflatable dude who gets power-ups. How can you go wrong?
And/or Super Metroid. Maybe my favorite game ever.
Mario 3/Mario World are solid calls. If you like puzzle games, the Lolo series is awesome. And Zelda 2 is still underrated.