House
Stop watching after: Season 4
Total number of seasons: 8
While many of the jokes in the show aged rather poorly, early seasons of House were undoubtedly entertaining and worthy of the prominent spot that the show occupied in the television landscape of the time. Hugh Laurie is brilliant was Dr. House, the supporting cast was strong, and the fast-paced format of the show with its self-contained episodes were a great combination. However, after a very emotional fourth season ending, the show begins its slow but steady decline, as supporting characters come and go and the plot lines get more linear and less engaging.
The fifth season also marks the beginning of a certain plot line that ends up taking over the show. According to Entertainment Weekly (warning: spoilers in the full article),
Not only did [the plot line] make House a worse doctor, but it also made House a worse show… [It] went from Sherlock-solving-medical-mysteries to Sherlock‘s Anatomy. It took everything that was interesting about the show—Laurie’s performance, House and Wilson’s relationship, the medical cases—and made them secondary to whatever [drama certain characters] were having at the moment. […] By making [the plot line] the center of the action, the show no longer stood out among the pack. It was just average, and that was one adjective never used to describe Dr. House.