WhatCulture has already talked about a few shows that have jumped the shark or should have quit while they were ahead here and here. So consider this an ongoing series of shows that arent necessarily shows that should have been cancelled but more shows that became victims of their own success or shortcomings. The early seasons of these shows are what made them what they are today, which unfortunately is usually just a shallow imitation of their early years. Perhaps you could split these series up like Law & Order; one half is the set up for all that made these shows great, and the second half is the semi-lame reason why some people just consider these shows 'okay'.
8. Californication
Must watch Seasons 1-4Or just start watching from Season 5 and pretend you totally get it. David Duchovny was absolutely born to play the role of Hank Moody, a New York literary libertarian turned Hollywood wannabe screenwriter. The first four seasons are a hilarious X-rated romp through the libido (and liver) of Hank who basically drinks constantly and screws every woman he meets in LA despite trying to win back the love of his soul-mate Karen and their daughter Becky. The first four seasons of Californication follow a tremendous, well-detailed story arc that starts with Hank bedding the under-aged daughter of his ex-wifes new fiance and with the threat of this underage rape hanging over his career manages to maintain your interest for four seasons. Helping matters is the intense sexual comedy that Californication provides. The tight cast of Hank, Karen and best friends the Runkels plus an amazing assortment of guest stars such as Callum Keith Rennie as a Phil Spector-like party animal/music producer, Katherine Turner as Runkel's sexually harrassing boss, Rick Springfield as himself plus some of LAs best breasts leads to some of the best adult-oriented comedy Ive seen that doesnt pander down to the audience's intelligence. What other show has someone go down on a woman by accident or show a threesome with someone (Hank) obviously not really in the moment, not that it matters. At the end of season four, it ends perfectly; the story arc started in the first episode is finally resolved and all story arcs come to an end in a way befitting the entire series. In Season 4s final shot Hank is seen driving off in the sunset in true Hollywood fashion and there could be no better way to end the show. BUT Sadly, most likely due to it's immense success and the all-important ratings, Californication was brought back to a shadow of its previous self, despite having all the main characters again. Season 5 tried to start the series anew, scripting a 3 year absence from LA for Hank Moody who once again comes back and tries to reassert himself into Karen and Beckys life. It's difficult to re-invest in a series that ended so perfectly after Season 4. It's like your best friend has left you to pursue their life in the big city, leaving you sitting alone at the pub nursing a pint then to discover them 2 months later sitting once again on the barstool beside you. It's that scene between Matt Damon and Ben Affleck in Good Will Hunting where Ben finally tells Matt that he hopes one day he won't be there to be picked up to go to his bad job. Hank Moody was/is your best friend who was never going to be the one to stick around and that was okay.