In general, the games I put at the top of my "Best Ever" list, are by their nature stipulated as games I can go back and play almost any time, unlike most other games where I have to be in the right mood to play them:
SMB3, SMB1, Mega Man 2, Kirby's Adventure, Super Castlevania IV, Super Metroid, Final Fantasy II (IV), Bust a Move (more or less any of em), Tetris, Mario Kart 64 (for multiplayer at least), Goldeneye (same), Adventure Island II, Mighty Final Fight, Street Fighter II, etc.