I've been looking for a good computer game (that I would like), but don't know of any more. My favorites have been:
The old Infocom games back when they were popular.
All of the Myst game series
Syberia and Syberia II
Mystery Island and Return to Mystery Island
The Kings Quest games.
And a few that I can't remember the names of.
I don't play adventure games often, but I have good memories of Kings Quest games. Here's a list of popular ones with decent reviews... although I haven't play them myself. As far as I know these are all games on PC.
The Longest Journey
The Black Mirror
Shadow of Destiny (my brother enjoyed this one)
Also, as much as I despise IGN, they do list games by category so you can always check there for any newer adventure games.