Well, I guess Sierra, even though LucasArts is pretty close. Sierra made the GKs and the King's Quests and I prefer a really mysterious and deep story more than the more humoristic and maybe a little less deeper ones that L.A. makes... I'm not saying that I don't like the L.A.'s stories, I love them, but I just prefer a real, real, real enigma...
OK, Leisure Suit Larry might not be such a mysterious one, but that doesn't count...