Here's a "top" 5 list for NES & SNES you should play, one for Nintendo brand games, and another for 3rd party (I'll omit FFs).

NES-Nintendo
Super Mario Bros.
Super Mario Bros. 3
Legend of Zelda
Metroid
Super Mario Bros. 2

NES-3rd Party
Castlevania III: Dracula's Curse
Ducktales (Woo Hoo)
Chip & Dale's Rescue Rangers
Super C
Contra

SNES-Nintendo
Super Mario World
Zelda: A Link to the Past
Super Metroid
Super Mario RPG
Yoshi's Island

SNES-3rd Party
Super Castlevania IV
Mortal Kombat II
Street Fighter II Turbo
Magical Quest Starring Mickey Mouse
Robocop vs. Terminator