Season 8 is where I threw in the towel. I wasn't massively invested in it and was just watching it as the missus was but after the fallout of the plane crash I actively did something else while she watched it. Absolute fucking garbage.
I remember Breaking Bad being excellent after the end of S3, but there was an awful lot of filler there before that. This is the problem when they make 22 episodes a season because of advertising revenue. I don't think I could get through all of it again.
Surprised noone has said the Simpsons yet. Around season 8ish is where the good ends. When they started the formula of completely random events in the first ten minutes compared to the last twelve is where they lost me. They traded humour for wackiness and it was shit.