I've been thinking about the difference between prestige high quality TV Shows and the things people call « basically a ten hour movie ».
The first, I think, is length. Most great series nowadays have adopted more limited formats than the old 24 40 minute episodes per season. However, most of those shows still have multiple seasons whereas I think serialised movies need to be more constrained. A single season sounds like a good rule of thumb, and it probably shouldn't stretch beyond ten hours either.
Then there is the structure. A typical movie has one major (or a collection thereof) arc that can be divided into a number of acts. TV shows on the other hand, even though they tell a story that spans the length of the season, or indeed the entire show, are also episodic in nature, and must abide by the rules of that reality. Every episode must have its own rhythm, an inner balance of the series' idiosyncratic elements, and cliff-hangers at the end are ubiquitous. I am tempted to say that the more a series obeys this rule the less like a movie it is.
True Detective is a good example of a show that works quite well when you consider its episodes separately. Two of the first series that came to my mind for this Top 5 were the mini series Mildred Pierce and Parade's End, two long adaptations of novels. While I am sure there was sound logic behind the separation of both stories into separate episodes, I remember only the stories and not where the cuts were made, whilst I can remember distinct endings of True Detective or Game of Thrones episodes.
I am watching two other shows right now that seem to work quite well as long movies - Patrick Melrose and A Very English Scandal. I don't think however that this category is constrained only to mini series and adaptations. I am still trying to figure out how to parse them out.