Hmm I missed the "all platforms" part. I know the Longest Journey, actually I played the demo and waited for a year for the english version to be released and got it as well. Unfortunately I didn't have time to complete it, but I still keep my savegame near the beginning of the game and would like to play later. As far as I remember, the voice actress of the protagonist was better in the demo than the retail version.
Another good adventure game is Sanitarium. It offers a little bit sick but distinctive experience.