I finished Legacy of Kain: Defiance and thereby finished the series.
The game switching between Kain and Raziel each chapter was a fun move, considering they were both doing essentially the same tasks in different periods of time, playing into the theme of the "circle of destiny" that Kain said both he and Raziel were forced upon. The more the two of them tried to defy their fate, the more fate was forced upon them, neither character totally sure if the choices they were making were of their own volition or the hand of fate turning them. The revelation by Kain that Raziel is the only being who truly has free will, since he was killed and resurrected--his soul no longer being in the "wheel of life"--was totally fascinating. Raziel does eventually kill Kain, as he was instructed to do by the Elder God in Soul Reaver, but it doesn't play out the way any of the puppetmasters think, not even the Elder God who boasted about setting everything in motion, leading to one of the most satisfying moments in the series. Raziel is defeated in battle and resurrects in the spectral realm where he is taunted by the Elder God. Moebius speaks with the Elder God in the physical world, while Kain, resurrected by means unknown to him, Moebius, and the Elder God, stumbles upon Moebius, and finally kills him. Seeing Moebius' soul come into form in the spectral realm, Raziel devours it, denying Moebius the privilege of being reincarnated. It was a satisfying end to a real bastard of a villain.
Raziel finally defies fate and acts of his own free will, sacrificing himself to form the complete Soul Reaver blade, to Kain's utter dismay. Though Raziel spends much of his screen time despising Kain, Kain never refers to Raziel as an enemy or even a pawn. It was satisfying to see Kain so distraught once he realized Raziel was sacrificing himself to empower Kain. Raziel's sacrifice binds him, the spectral Soul Reaver, to the physical Soul Reaver blade, healing Kain, and giving him the power to harm and battle the Elder God. He doesn't kill the Elder God, but leaves him, with the knowledge that Kain could kill him, and the Elder God is furious that his godhood is as fragile and fleeting as any mortal's life. With this, Kain is finally free from the wheel of fate himself--he has finally defied fate, even if the pillars were already shattered and ruined. The game closes on one final remark from Kain, saying that Raziel had given him something he'd never had before--hope. The game doesn't exactly end on a true final, definitive note, but it doesn't leave itself open for a sequel as hard as the other games in the series do.
Raziel and Kain both finally defy fate, in the form of defying the hideous god that boasted about controlled their destinies.
It was a great game and a great series. Each game went through its own little bit of development hell and I assume Eidos didn't want to make a sixth Kain game, but it's a great place for the series to leave off. I think the best one is still the original Soul Reaver, but the story is so strong throughout the series that I would honestly recommend the entire series in a heartbeat. Each game is fairly short and mostly unchallenging, getting through the entire series takes the same amount of time a single more modern game would take to finish.