Series 1 and 2 of Sherlock are excellent.
Series 3 and 4 feel like shitty fanfiction sequels.
this is true also
JEDIT, but i blame the problems of everything after Series 2 on increasing time between series, and the extreme complication that Moffat tried to put into every single plot. Its like he became obsessed with making every single plot more clever than the last, and the Series suffered because of it.