While some find the level design to be a step back from 1, I disagree, the frustration it can add certainly creates tension, but in a way that benefits the games story and themes tenfold.
The story is both deeply layered, interesting, and proves its point in such a beautiful manner.
The Soundtrack is possibly one of the best in gaming, and the muddy grungy graphical style helps sell this bleak world incredibly.
One of, if not my favorite game of all time, certainly one of the most influential pieces of art I have experienced in my life.