Darker than the first and better than the rest, Dark Knight leaves more then a chilling aftertaste in the brain. "Why so serious? Why so Serious? Let's put a smile on that face!" Anybody who heard the Joker (played by the late Ledger) say those words knows all about the chills that go through the body and mind each time you remember.
With adding a couple of spices to the earlier created Joker by Jack Nicholson, Ledger soars beyond all expectations, making this Joker the ultimate villain of all time.
What's there besides the crazy caked up clown? Plenty of things Christopher Nolan never seems to run out of, nor bore or disappoint with. The movie may run over two and a half hours, but if it didn't it simply wouldn't get its point across. The ultimate battle between good and evil cannot be done in the matter of any time less than that. Everything is explained, but not fully. And everything seems to be right and predictable- until it isn't.
Christian Bale soars with his character once again. That deep voice that comes out with the BatSuit and the slightly naive charm make for the ultimate good guy who confused about whither or not it's time to fold his wings.
Must not be forgotten the great Harvey Dent or Two-Face, created but slightly destroyed as well by Aaron Eckhart. This guy rises up to the challenge of gone-crazy-without-his-love-man, only to drop extremely. Whither his character's wickedness is less threatening in comparison to Ledger or on his own accord is still unconfirmed.
Maggie Gyllenhaal is perhaps quite a step-up from Katie Holmes but most certainly not in the 'better acting' direction. Enough said.

There's not much left to say, but see it. If not for the fan in you, then for the curiosity of how much one man is capable of- of both good and bad.