I never watched any of these series before The Sopranos. After getting into that, I watched Dexter, Californication, then a bunch of them.
GOT is one of my favs but there are a lot that take up the slack while you're waiting for next season. This coming Boardwalk Empire is the last season for it.
Rome was excellent!
Homeland was interesting -- and doubly so now with reference to Bowe Bergdahl's retrieval. They should run that series again.
Band of Brothers is one of the best tv productions I've ever seen. They run it back-to-back during Memorial Day weekend and I look forward to watching it year after year.
Lark Rise to Candleford was a wonderful BBC series. (I bought the CDs.)
Downton Abbey is another superb BBC series.
Parade's End is yet another example of BBC's matchless theatrical skills.