Sherlock Holmes: A Game of Shadows (that is, a sequel to a refreshingly awesome blockbuster) wasn't a total piece of crap, trying to quickly cash in on the success of the first episode.
Sadly, in the last ten-or-so years I've became used to being disappointed by sequels. Matrix, Pirates of the Caribbean, Transformers, to name but a few. I thought that's just how it goes, that the times, when the sequels of a great movie were almost as good (if not better), were long gone. And then, this.
Don't get me wrong, it's not as good as the first Sherlock Holmes movie. But almost. And it makes me happier than it probably should.
I don't think it's a miracle at all. Many times the first sequel is better than the original, because there's more of an expectation and more riding on it, and the confidence of everyone involved in the project is higher. The Dark Knight, Pirates of the Caribbean 2, Godfather 2, The Empire Strikes Back, Toy Story 2... all better than the original. I think where you're more likely to have problems is with the third film, because by that point everyone is cocky and just phones it in. Granted, there are plenty of examples of sucky first sequels, and a few examples of good second sequels (Toy Story 3), but anyway, it doesn't surprise me anymore if a sequel is really good.