I kind of answered this on Day 3:
The main reason I hate The Killing is because it had so much promise, being based on such a good show. It started quite well, but that was mainly because it was following the original's plot. Once it started trying to branch out on its own, it became unstuck and the first (and so far only) season ended with a ridiculous twist just in an attempt to get people to tune in for a second season (which I hope never comes). Forbrydelsen didn't have to rely on such cheap theatrics, it just had a cleverly written plot delivered by a brilliant cast. There was a second season not because it threw in a twist at the very end but because audiences were hooked, and deservedly so.