I thoroughly enjoyed ALL of these series, they all had something different to offer: Daredevil was a really well made, generic masked vigilante story, just what you would expect and then some.
In Jessica Jones I liked the little nods to the conventions of Chandleresque Gumshoe stories, plus I also saw it as a whole as an allegory for spousal / girlfriend abuse.
Luke Cage was great fun, essentially a 70's blaxploitation flick where the protagonist has super powers and at the same time providing a rousing message regarding the state of race relations in America today, in particular to the relations between African Americans and law enforcement. In short the subtext was pretty heavey stuff!
Iron Fist was extremely silly and terrific fun. It didn't take itself too seriously and didn't try to be anything more than it needed be. A fun action melodrama.
Punisher was so grim and as others already said, it was made by Bernthal's performance (he truly is Thomas Jane's heir), with another actor it could easily have failed.
Then there's Defenders. That was awesome
EDIT: Almost forgot to say: I'm kinda hoping that Disney has only taken back the rights temporarily so that Samuel L Jackson can enlist the Defender's help in undoing the damage done at the end of Infinity Wars...