Takes about halfway through Season 1 for Agents of SHIELD to really come together, bout the time Winter Soldier came out, and the series tied into the MCU more solidly as a backdrop for the overall series storyline, but it's really solid now.
Season 2 AoS has been lights out, but Season 1 was so horrifically bad, I still hold a grudge against the showrunners for wasting my time for so many weeks. And I'll probably have to waste another week devising a season one guide, where I tell you what episodes are good, and important to following the season, and write summaries for the episodes to skip.
Arrow is pretty good once you get past the CW's penchant for having shows look like overly photoshopped supermodel showcases (and face it, the cast is pretty good looking, both genders). The main actor carries it well and the cast overall has decent chemistry.
I don't hold a grudge against actor/supermodels that can do a salmon ladder. Sometimes, the writers can stick in awesome snark, but usually not often enough. One of my problems with Arrow is that its basically cloning/coopting the Batman mythos.
Gotham is a pleasant surprise. It's quite good. And if you British cinema, you'll see Sean Pertwee as Alfred, one of my favorite British actors.
There are a (counting) gross of British actors that I think are measurably better that Pertwee, (most of them playing Americans on TV) but I do have a soft spot for him, in his limited roles, and that he's Jon Pertwee's (Doctor Who #3) kid.
He does quite well as Alfred, and I'd even argue he'd make a good choice for the movies as well, though he might be a bit young to play Alfred to an adult Bruce Wayne. The show overall again has a good cast with good chemistry. And it didn't have the shaky/cheesy start that SHIELD did, finding its footing right away in the pilot episode in my opinion.
My problem with Gotham is that I think the ideal Batman TV series needs to be TV-MA on a subscription cable network, and that DC doesn't have the guts to put out a truly artistic rendition, so they will destroy it with half-measures like Gotham. Its much like how corporations have destroyed Christmas as an enjoyable holiday. And Robin Lord Taylor (Penguin) is the only actor truly keeping the show afloat. It would be a mistake to introduce the Joker in the 1st or even 2nd season, but that show needs more than RLT to be worth watching. They can't carry that show with one-shot comic-like villains each week.