Sherlock was a groundbreaking detective series that modernized adaptations of Arthur Conan Doyle's Sherlock Holmes books, featuring feature-length episodes detailing the exploits of the eponymous genius detective. The show featured Benedict Cumberbatch as Sherlock Holmes and Martin Freeman as his companion, Dr. John Watson.

The four seasons of Sherlock varied in quality, with some being better than others. The show received wide acclaim, but as it progressed, it began to wane in later years. The unfavored special in 2016 only added to this sentiment.

Season 4 delved into Sherlock's family history, focusing on the psychological schemes of his sister Eurus Holmes, leading to a tragedy that illuminated the complex dynamics of the Holmes family.

While it had some highlights, such as the return of Sherlock's nemesis Jim Moriarty and the depiction of Eurus, the season suffered from a continued focus on character development over the plot, which undermined the central mystery essential to each episode.

Season 3 continued the trend of focusing on character arcs and development rather than establishing a compelling central mystery within the plot. It featured Sherlock's return after faking his death to dismantle Moriarty's criminal network and introduced a new adversary, Charles Magnussen. The extended sequences in Sherlock's mind palace were a highlight, but the season also had moments that felt like an anticlimax and wasted potential.

The first season of Sherlock was nearly flawless, showcasing the main characters and delivering intense action. It introduced the modern-day detective duo as they investigated their first cases and adapted three classic Arthur Conan Doyle tales. The only weak entrant was "The Blind Banker," but overall, the season was a thrilling and enthralling string of episodes.

Season 2 was the strongest in the series. It included the return of Sherlock's arch-nemesis, Jim Moriarty, whose elaborate schemes threatened not only the detective's life but also those he cared about. The gripping narrative explored themes of friendship, betrayal, and the consequences of Sherlock's unconventional methods.

Overall, Sherlock season 2 was the best overall season, with a solid run of episodes, characters, and plots.

In conclusion, while Sherlock had many fantastic episodes, the quality of the seasons varied. The show was notable for infusing action into the updated sleuth's narrative, combining it with witty humor and deft storytelling. Despite the decline in later years, Sherlock remains a groundbreaking and influential series in the detective genre.