I'm a sucker for pretty much any superhero related show, so I started with Arrow when it first started. I agree, if you're not into the pilot, you probably won't be into the rest of the series. It does get better, but it's still gonna have the same "vibe" or whatever. And it definitely had a dip at some point -- I don't remember when, but it defintiely went down. It picked up again and is back on "course". The thing I fast forward through are all the angst-ridden "conversations" -- it's playing to a certain demographic I'm not a part of -- well, this show already starts off not catering to my demo, but that part is WAY not my demo.
The super-hero shows on right now would include:
Arrow -- I like it with the caveats above
Flash -- it takes it's cue fromt eh comic in being more "light" that "dark"
Agents of Shield -- I think this one has improved each season
Agent Carter -- I liked this one right off the bat
Daredevil -- I'm not super excited about the casting for DD himself, but I thought everyone else was good. I liked the series and look forward to the next season
Jessica Jones -- so far I'm liking it. It's taking it's time, but I'm not bored. Definitely the darkest of the bunch
Heroes Reborn -- so inconsistent. doesn't have the magic of the first season or two, but not as bad as the last of the original series
Gotham -- I watch it. It's got some good episodes and some bad.
Supergirl -- I've only seen the first episode and I liked it ok. I think the lead is well cast, i'm less thrilled with Calista Flockhart as the boss (maybe I'm just tired of the bitchy devil-wears-prada trope) and am violently against the Jimmy Olsen casting (Jimmy Olsen was supposed to have a certain level of innocence - that characteristic is completely lacking with Mehcad Brooks)
Sense8 -- Haven't seen it yet, so have no opinion.
Did I miss any that are currently airing?