Let's see.
The Simpsons - I only finally saw some episodes of Season 19 as it was on TV and I mostly had them on mute after a couple of episodes. I think at best one or two episodes were funny, which makes me grateful that I barely saw anything after Season 10-ish when they first aired. The problem is that the show has fallen into the Family Guy factor of putting jokes before a good story. I'm glad Channel 4 airs earlier episodes on the weekend because it makes you appreciate the humour, timing and plots of the episodes. I remember how in a 10th anniversary documentary they said how they tried to be realistic with the moment to lead into a joke first then let their imagination run wild, there's nothing like that in today's show. There's a lack of subtly or charm, and just feels like they just want to break a record now for the sake of it.
Family Guy - Like some people here, I just fizzled out around Season 7/8, as the show just wasn't enjoyable any more. In the past I would sometimes just put Family Guy on the background because I could do stuff, then laugh at a funny moment. But now it just makes me feel meh. I've some episodes since Season 7 & 8, and they have some average episodes, but other times it just ends up being a void, or just a repetition of a better episode from earlier on, like the one where Lois took up boxing, the plot was a repeat of a better Season 3 episode with her doing karate.
The Big Bang Theory - I'll be honest and say I enjoy TBBT, but like Барбоса said, it's just too repetitive. What doesn't help is E4 just choosing to start from beginning once it reaches the end of Season 4, so it's hard to tell when a new episode is a new episode and I'll somehow end up encountering the same episode for the 5th time in a fortnight. The question that comes up is what TBBT episodes stand out, and it always seems to be a guest star episode because it involves someone else outside of the regular cast members. The problem that it has is that it has become like Friends and has made the characters fall into typecast models of themselves, limiting themselves and losing development overtime. The other problem is that the main dynamic of Leonard and Penny's relationship is self contained that it truly has run out of juice for anything more, I have yet to see any of Season 7 yet, but they need to decide what direction it's going with them and finalise it because it's not carrying the show and their reliance on Sheldon to carry the rest of the episode doesn't help.
American Dad - I've only just been watching more of it of late, and honestly, it is much more enjoyable than Family Guy at times. The main problem is that they heavily rely on Roger for some episodes, and honestly, I don't find Roger to be that entertaining of a character. Granted, he has had some good moments, but he's just a one-trick pony.
Agents of S.H.I.E.L.D. - I'm sure people here find AoS to not be good, but given it's been given the go ahead for a full season, and it has lots of fans, I'm going to add it in here. It's only four episodes in and I find it average with some entertaining moments, but that's it. The problem is that it doesn't have an arc or a potential threat (though Episode 4 seemed to hint it's finally happening), not to mention that the team isn't believable and needs something more, especially given the impression that S.H.I.E.L.D. gave us during The Avengers, they seemed more than just folks who live in a plane that is like Serenity from Firefly (I love Firefly but this show does give heavy FF vibes at times). The other problem is that this meant to be an agency, but half the team are rookies and someone who hasn't chosen her allegiance to the team (not to mention the least interesting of the lot), there's a lack of discipline amongst them to say 'Don't mess with S.H.I.E.L.D.', I just hope it does get better.
I still need to watch Breaking Bad to form an opinion, and I started Game of Thrones recently and enjoyed that a lot. I only just got Netflix so I'm still trying to decide what other shows to watch.