It may be hard to imagine now, but back in 2009 many were predicting Gatiss and Stephen Moffat's modern day reimagining of Sherlock Holmes to be a potential flop. Moffat's equivalent modern reworking of Jekyll And Hyde (in which Gatiss had a small supporting role as Robert Louis Stevenson) hadn't really set the world alight; Sherlock's only star power came from Tim from The Office, featuring opposite the odd-looking funny-named guy who played the rapist in Atonement; and an expensive pilot for a series of hour-long episodes had had to b been completely reshot. When it eventually aired in the summer of 2010, however, it quickly became one of the BBC's biggest hits.
By the time that the three-episode season had concluded with the Gatiss-penned The Great Game, in which we were introduced to Sherlock's arch-nemesis Moriarty in a series of devious puzzles that led to a cliffhanger conclusion, audiences were completely hooked.
Sherlock cleverly updated aspects of stories, characters and tropes from both Arthur Conan Doyle's books and previous adaptations and wove them into something utterly contemporary, fast paced, intelligent and full of sharp dialogue. The series' take on the legendary detective as a "high-functioning sociopath" in a stylish coat made Benedict Cumberbatch a star, paving the way for Oscar nominations and Marvel superhero flicks.
While it is kept from the top spot here by the fact that the later two seasons struggled to maintain the quality of the earlier ones, creaking under the weight of expectations and becoming excessively self-referential and clever-clever, Sherlock nevertheless remains one of the landmark TV series of recent years.