The reason why I loved SoT so much was how much Persian culture was embedded in it. There are quite a few remarks made by the prince regrading Persian mythology and these bits of dialogue really made the game for me. Also, the Persian architecture that was used in the game. I have been to such places in my various trips to Iran and visited older cities that still retain some of the old architecture and I was amazed to see it used so well in SoT. Also, the brilliant platforming and the puzzles made the game excellent as well.
Warrior Within still had the brilliant platforming but the puzzles were non-existant and the combat, even though improved, still relied far too heavily on button mashing. I didn't really care for the metal or the gothic influence that the game had, but some of the music in the game is very well done, and if you can look past the gothic influence, it is a fun game. Still has its problems, but that's more with the content and style of the game.
I'll check into PoP 3 when it drops in price. Hopefully the stealth bits aren't overused in the game.