Breaking Bad is obviously the answer. There's no contender I've seen that comes close. And no, Game of Thrones isn't even close. I've watched every episode, I haven't read the books. From that prospective (ie: I'm not someone who is filling in missing awesomeness with my own memories), the show is mediocre at best. For every Red Wedding, there episodes focused almost entirely on a character I couldn't care less about (because there is zero backstory or personality to him) torturing another character I couldn't care less about (since he's an entitled, whiny, throw-away character). Or episodes focusing on some dumb red-head witch. Really, the show has about 5-10 characters who are great to follow and scenes with them can be spectacular. Unfortunately, there are about 50 characters in the show. Also (again, if you HAVEN'T read the books, this is a huge issue), there are a number of plots/subplots which are told in the wrong order. Many of the stories have gone, "look at this!" and there was nothing interesting there, or characters being referenced had never been introduced/explained why I should care. Then, after the "big reveal" scene, they go back and say, "oh yea, here's what we were just talking about, so now take this info and think back to the scene you just watched. ISN'T THAT AMAZING?!?!" .....No, it wasn't amazing. It was boring/confusing. Then, you explained things, so now I at least understand, but still get no joy out of it since that time has now passed.
As for Breaking Bad, as much as I love the show, think back to any scene featuring Walt's family, where no other characters were involved except for maybe Walt. They were ALL AWFUL. Every last one. Or how about the, "Walt's sis-in-law's a shoplifter!" subplot. Thanks for that filler crap guys, that really paid off. Thankfully, the majority of the show doesn't have any of that and for people watching for the first time, I just tell them to skip those parts and they're in the clear. But unfortunately the show isn't perfect.
As for Breaking Bad, as much as I love the show, think back to any scene featuring Walt's family, where no other characters were involved except for maybe Walt. They were ALL AWFUL. Every last one. Or how about the, "Walt's sis-in-law's a shoplifter!" subplot. Thanks for that filler crap guys, that really paid off. Thankfully, the majority of the show doesn't have any of that and for people watching for the first time, I just tell them to skip those parts and they're in the clear. But unfortunately the show isn't perfect.