North & South was excellent! (Mmm, Richard Armitage. :D) Also, Bleak House. I wouldn't say Desperate Romantics was the best drama I've seen, but Aidan Turner makes up for some flaws, and it's quite emotional. I've heard very good things about Lark Rise to Candleford and Death Comes to Pemberley, though I haven't seen them yet.
If you're into legal shows, Garrow's Law was very good. And on the dark, crime end of things, Ripper Street is amazing-- and just got saved from cancellation due to fan campaigns, which is pretty cool. But it's definitely not for the faint of heart, so that should be said.