what type of series are you looking for?
my recent favourites are: Barry (HBO), Warrior (Cinemax), The Good Place.
if you're looking for comedy, and have already watched the classic ones like HIMYM, Friends, TBBT, The Office, etc. then you can watch Modern Family, Parks and Recreation, Community. Or if you want something different, check out Wilfred, Santa Clarita Diet, American Vandal.
in animation, check out Gravity Falls, which is a bit childish early on, but gets great when the mythology expands. Rick and Morty is also great but you've heard of that most probably.
my favourite genre is time-travel, the best of those that I've seen are: 11.22.63, 12 Monkeys, Dark.
some other fun series are: Justified (action+comedy), Banshee (it's like a B-grade movie done to it's best form), Fringe (mystery solving), Terriers (comedy-crime drama).