For me it's Chrono Trigger. I always want to play it. I want to show it to my children. I hope it will be regarded as a masterpiece for generations to come.
Tetris. Straight original is so simple accessible and addictive. I really haven't cared for much else they done with it since. It was perfection also out the gate.
Also, Castlevania: Symphony of the Night. I can play it anytime, anyplace. The gameplay, music, graphics even today just feel so go for being 2D