We're normally latecomers to the big series.
From last year Sky Atlantic repeated all 8 Sopranos series so we caught up with them all then.
Recently we've watched:-
Game of Thrones - still catching up after downloading series 1 and 2
Continuum - SyFy time travel series.
Dexter since the beginning
Revolution - stopped after realizing all the episodes were becoming the same.
True Blood - we got fed up after 4 series
Hannibal - we watched the first 3 episodes and decide that it was not for us.
Oliver Stone's Untold History of the United States - fascinating viewing
American Horror Story - both series were really very good.
Elementary - modern American take on Sherlock Holmes - another excellent US series
Playhouse Presents on Sky Arts - a bit patchy but there have been some excellent plays.
We actually watch very little live TV and tend to "timeshift" a lot of it. Also realized that most of these are US series but with the noteable exception of "Utopia" most UK output seems to be dreary cop/murder thriller stuff.