I thoroughly enjoyed watching Downton Abbey. The entire cast is lovable, even the villains. The writers really did a fantastic job making even the smallest screentime character memorable.
The series follows a traditional Duke's family and household, and their emergence into the modern era. Throughout the series, we see the Crawley family and their servants handle the aftermath of the Titanic sinking, the first World War, several uprisings in Ireland, women's rights, the jazz age, and the fall of the great houses of England. We watch them struggle with change and fight for what they believe in and for each other.
If you want to watch a well written and beautifully shot drama of the early 1920s in England, this is your show.