Have you seen The Americans? Quite possibly the best TV series I've ever seen.I've watched 2 eps of S1. It's good but I don't think it's great.
I need a must watch series. I loved Mad Men but I couldn't get into : The Sopranos, Entourage, West wing, Dave, Silicon valley among others.
There's a BBC cop drama on Netflix at the moment called Line of Duty. I've watched the first 2 seasons and it's very good; the second season especially. But I'm a big fan of BBC cop and espionage dramas. I rank Spooks right up there with The Americans.