Grargar: Enebias, we are talking about GOG's
best-seller list. What is the first game that you don't own from there?
See what happens when you are illiterate? :P
I though we were talking generally about famous best-sellers on GOG (hence why I mentioned Monkey Island), not famous best sellers on the list with the same name (then I added non-GOG ones just because)!
zeffyr wrote it clearly, though, so... my apologies! Too much beer, I guess! :P
So, let me answer properly: the first game I'm missing is
Dungeon Keeper 2. I still have to play the first - gently gifted to me by GOG and EA during the last Valentine day- before considering a purchase, though.
On the same page, I don't own Theme Hospital, Neverwinter Nights 2 (I'm very interested in Mask of the Betrayer, but not as much for what concerns the rest), Heroes of M&M 3, Arcanum and many, many others.
The only one I'd really like to play is Freespace 2, but I always pass for a reason or another, mostly because I don't have a joystick.