Only ten years after The Secret of Monkey Island, the once-beloved adventure genre was dying. This was one of the last great point'n'click adventures, and after it... Only darkness.
Very long conversations (is that a bad thing?), mature themes, a beautiful soundtrack (which is available in mp3 format), 3D characters in prerendered backgrounds, oldschool puzzles with good adventure gameplay... and above all, a great story that pulls the player into the game.
If you like adventure games, you'll probably enjoy The Longest Journey. There's also a full 3D sequel, Dreamfall: The Longest Journey (confusing title! Why didn't they just call it "TLJ2: Dreamfall"?), but this is the beginning of the journey. They don't make games like this anymore!