There are great games and there are games that really make you say "Thats why I love videogames."
Here are the list of videogames in which impacted me as a videogame player.
Duck Hunt (NES) Thats why I love shooters.
Mario Bros. (NES) Yeah its good to jump on shrooms.
Metal Gear Solid (PS1) Games can have good stories? Wow.
Resident Evil (PS1). Holy Sh*t, that scared the hell out of me.
Halo: Combat Evolved (XBOX). FPSs are good on consoles! Take that PC gamers.
Grand Theft Auto 3 (PS2) I can do whatever I want, hell yeah.