Gabriel Knight was the brainchild of Sierra game designer Jane Jensen, who had previously worked with Roberta Williams on Kings Quest VI with great success.
This game..this game is extraordinary. Throw everything you know about "game plots" out of the window and realize this game has characters and a plot that quite simply put pretty much every other game in the genre to shame in terms of their reality, depth, and maturity of outlook.
The game's title character is famously voiced by Tim Curry, but the entire voice cast is world class, containing such names as Mark Hamill, Michael Dorn, Efrem Zimbalist, Jr., and many others. Few games are this well acted.
The game also uses a late-iteration SCI engine, and really contains some exquisite 2D art that pretty much outshines both the quality-but-90s-FMV-crude GK2 and the early-3D-crude GK3. Sins Of The Fathers was made with years of experience in 2D art, and it shows.
If you have any love at all for point & click adventure games, you simply must play this game. It's that simple.