My top 5 series in recent memory, in no particular order, are: Peaky Blinders The Fall The Wire Luther Breaking Bad What should I watch next?
Not sure what you've seen in the past. A bunch of HBO series are great. How about The Shield? I never watched that and recently started on the first season and it's really good.
Check out The Missing on Starz. Season 1 ran last year. http://www.rottentomatoes.com/tv/the-missing/s01/ Psychological thriller about a father's years-long quest to find his 5-year-old son who disappeared during a family holiday in France.
I've been watching The Knick. It's about a group of surgeons in an early 1900s New York City hospital. Absolutely fantastic if you have even a passing interest when it comes to the history of medicine. Cinemax originally had it, but its on HBO GO until the end of October.
Mr. Robot--currently airing, my favorite show since Breaking Bad. It's generally about a mentally ill hacker. Orphan Black Hannibal True Detective Humans Utopia--UK show
Veep doesn't get enough love on this forum. Funniest show out there. If you want a more serious show, Mr. Robot, Orphan Black, True Detective Season 1 (Stay as far away from Season 2 as you can) do the trick.