Cool. I got this for free recently. I'll make sure to check it out when I have more time.
For me, it's the Legacy of Kain Series. Specifically Soul Reaver 1&2. I don't know why more people haven't played this one. Excellent adventure game (though combat in the second one can grow stale), a suprisingly intricate plot with good twists and turns (in a good way, not a Metal Gear Solid 2 way), and hands down the best voice acting in any videogame ever. SR2 is on my list of top 5 games, though the others on it are more well known.