My favorite game of all time will always be Final Fantasy 7. Yes, that means I am pretty old!
Playing FF7 at age 13, I was just blown away by the size/scope of it all. Up until that game, I'd primarily played sports and action type games.
I've played many RPGs since trying to rediscover that same feeling, and none have hit me quite the same way.
Later on, I came to really appreciate the soundtrack too, which is still in the rotation of music I listen to while programming.