I just watched the finale of The Americans last night and I think of all the TV I've watched, it's moved into my all time Top 4. I think I have Breadking Bad, then Game of Thrones and then this tied with Justified.At the height of the Cold War two Russian agents pose as your average American couple, complete with family.
It's just such a good show, with very few flaws. Great story, great characters, great acting and things that really make you think. It's a rather serious show (as in no jokes or humour) as I think they try and depict how this really would have been. It's not about spies like a James Bond movie, it's all about their families and relationships as well as the missions they complete for the good of the USSR.
Add in that it has a great ending and it's a show I highly recommend. I think the first 4 (of 6) seasons can be seen through Amazon Prime at the moment. I'll give it a few years, then it will be on my list to watch through again, for sure.