Gabriel Knight, Hands down.
GK3 was iffy in spots, a lot of the puzzles weren't as integrated as they could have been.
GK2 was great though. Definitely the best FMV game that came out of that whole craze (though that's not really saying much). But the story and locations were cool, and the acting was actually pretty good.
I remember it annoyed me at first because I couldn't 'pick' what action I wanted to perform and it was all automatic, but then again cycling the right mouse button isn't exactly the epitome of gameplay.