Once you've done that, the new challenge is finding time to play so many great games!
On my own list, I chose a number of games because I felt they would best represent their series to somebody new. I love Return to Zork best of the graphic adventure Zorks, but most new players would appreciate Zork:GI better (or maybe Zork: N if they like a touch of horror). Gave the Myst series more than one slot, but then I really love Myst
Mostly I chose games a newer gamer could reasonably hope to find. Celtica wouldn't be fair to list when its hardly available anywhere. I probably shouldn't list Starship Titanic for the same reason, for example, but I really did enjoy it that much! Maybe the new person will see it at a 2ndhand store or something. It does happen!
Mostly chose the first of two games when original & sequel are just about as good (Syberia, Darkfall, RotS, Broken Sword, etc). I figure if they love the first one, they can find about about the 2nd one afterward.
Nancy Drew was the hardest choice. It would have been a serious omission not to have named at least one of the games in a series I have enjoyed so much, but it really was very hard to pick just one.
Susan