Pokémon Red/Blue, Pokémon Crystal
Doom (1993), Doom 2: The Plutonia Experiment
Quake, Quake 2
Prince of Persia (the MS-DOS one)
Metal Slug 1 and 2 (these came out almost 26-28 years ago)
Contra, Super Mario Bros, Hudson's Adventure Island, Kirby's Adventure (all of these for the NES)
The game that for me is a masterpiece: Super Metroid.
After that, a few much less known: Montezuma's Revenge, Boulder Dash 1 and 2, Keystone Kapers, Choplifter, River Raid and Henry's House, all of these for the Atari 800XL.