I think it's really a brilliant move - since a) as long as you can get Netflix you can watch the shows whenever - which means that you don't need to worry about waiting for Hulu or ABC.com - plus if they do it like they did their other Netflix shows, we're looking at like a season of TV coming at us all at once. b) They can be a bit more PG-13/R if they wanted to - I doubt they will - but like Luke Cage - honestly the man was originally Blaxploitation fodder. So even if they have him drop a rare motherfucker line - it won't be that shocking. Plus I'm sure SLJ would love to show up and drop a motherfucker line himself in character as Nick Fury. c) Its not dependent on ratings. You won't get a half season of say Jessica Jones just because the ratings weren't where the network wanted it because Dancing With the Stars or Football or something political interrupted its airings and they just look at the ratings being 'dismal'.
Daredevil, Iron Fist, Luke Cage, and Jessica Jones are plenty for a 'test the waters' plus if they get enough buzz then maybe they'll feel better green lighting an actual cinematic movie with them later on - or including them in Agents of SHIELD or another Marvel Studios movie.
I wouldn't mind a proper Ghost Rider series on the level of say something like Supernatural mixed with a bit of say Knight Rider. Loner going around trying to do good but fighting super natural baddies. Personally I'd totally back someone like Charlie Hunnam from Sons of Anarchy/Pacific Rim as a younger Johnny Blaze. Or just do the whole Spirits of Vengeance thing with Charlie as a 'retired' former Ghost Rider and someone as Dan Ketch's Ghost Rider and they basically adapt the old Spirits of Vengeance comics from the early 90s