Only ones I end on bad terms...
Some examples:
Bleach - It started off really well but gradually declined over time. IMO Bleach reached it's peak around Soul Society Arc and it never got back there in terms of quality. Was it because it really wasn't that great anymore or because of that annoying 40 episode filler it slowly got repetitive and only reason I've stick with it as along as I've did was out of respect for what my memory of the show was during those first 50 or so episodes.
Fairy Tail - Fairy Tail was one of those anime I've never really understood, or rather it got storyline or storytelling that never really appealed to me. I've never got sense of progress watching FT, I wasn't sure what characters were after or rather I've never seen them do something about it. They'd just stroll from one adventure to another because Mangaka said so... Imagine how Naruto would look like if only thing he ever did was doing missions over and over again.
*That ending though *-*
http://www.youtube.com/watch?v=GW6po2_mWzQ
Both of these anime had awesome OST...
I'd never return to these anime because I know what to expect from them and I don't like what I'm getting. Sure I could watch like first 50 eps of Bleach again but I'd never watch the whole thing, with or without filler.