It's like a guilty pleasure haha. SAO is definitely a show I have so many things against, but continue to watch anyway. I mean I hated it to the guts during the first 12 episodes and still watched it every week despite the fillers. Naruto would be another one, though I read the chapters as well as watching the episodes. It progressively got worse and worse, but you can't really drop something that's near completion. The final one would have to be Blue Exorcist, that went so far off the manga into it's own story, and it turned out cheesy and horrible. But like Naruto, you have an obligation to finish something that you've gone so far through.
I think those would be the only instances. I very rarely drop things, cause I very rarely read/watch lots of things at once.