Here is a list of fantasy adventure games that might be enjoyed by King's Quest fans.
Adventures of Maddog Williams in the Dungeons of DuridianEdit
Legends of KyrandiaEdit
Quest for GloryEdit
Torin's Passage Edit
The Black Cauldron Edit
The Longest Journey, Dreamfall, and Dreamfall ChaptersEdit
Order of the Thorne: The King’s ChallengeEdit
Simon the Sorcerer Edit
Lure of the Temptress Edit
Shadowgate Series Edit
Zork Series, Enchanter Trilogy & Wishbringer Edit
Companions of Xanth Edit
Heroine's Quest: The Herald of RagnarokEdit
A Tale of Two KingdomsEdit
Hero of Infamous Kingdoms Edit
Ween: The Prophecy Edit
The Book of Unwritten Tales series Edit
American McGee's Series Edit
Darker takes on Grimm and Alice stories. These tend to be more action-adventure so might appeal to fans of King's Quest 8. Whereas Grimm is pretty much a action platformer with no 'deaths'.
Witcher series Edit
Yes its an action RPG series, but its also a dark fairy tale series with a dark sense of humor. Finding the references to classic fairy tales reimagined in more traditional manor might be of interest to some players...
Also if you liked KQ8 or similar RPG mechanics, its a very good modern take, with improved battle systems.