Assassins creed comes to mind for me right away. The first game's storyline was alright, though the gameplay was repetitive and boring. The second game redeemed almost everything from the first game, but there was something about it that I didn't much care for. I literally got to the point in the second game when you get the mask for that ball thingy near the end, and had every upgrade for everything and unlimited money coming in that I couldn't use, and was like "this game svcks." and put the game down, never to play again, and no desire to want to finish the story of the second game. I don't know what it was that really turned me off, probably the extremely easy gameplay with like 0 chance to fail.
I haven't touched the third, or any of those other games that came out between and I most likely wont ever touch another AC game again, especially now that they're like call of duty and come out with at least one a year. The games just feel like pumped out drivel to me with little effort put into the development, meant to appeal to young kids, much like the call of duty franchise.
For TV shows, South Park comes to mind right away. I was a die hard south park fan, and I think the seasons 1-10 are genius and were ahead of their time in terms of issues they were addressing back in the early episodes. After season 11 they started to go downhill, IMO.
I used to watch every episode of south park the day they came out, and keep up to date with the show. Now I haven't even watched anything of the last two seasons, just because it seems like they aren't even trying anymore, or don't care and just want to milk the show for money now.
Back in the day, their episodes were about actual issues, and threw out their messages through metaphors and the like, and you had to actually think about what the episode meant.
For example, off the top of my head, the Man Bear Pig episode with Al gore, the whole premise of the episode is that Man Bear Pig = Global Warming. Now if they made that episode it would probably just be like "Global warming is [censored]!" and just straight out say what they meant. There was more allusion to the points in their episodes back in the day, and now it seems that they think no matter what they write, it's gold. (think of the beatles in their later years, it seems that they too stopped trying because they were hailed as musical geniuses all these years, so they would come out with a song that they normally wouldn't release for being sub-par).
I'm sure I can think of a hell of a lot more, but those are the first two things that come to my mind of franchises, or series that I have no interest in anymore, but used to once upon a time.