Arrow - Spoilers galore
I can't comprehend at all why Flash is universally regarded as the better show?
Audiences seem to be getting tired of the grimdark, ridiculously angsty approach to stuff. Everything moves in cycles and while that kind of thing was very popular for a while, but people seem to want their superheroes to be a little more "super" again. Flash does that. It's got a sense of fun and hopefulness about it, but still has stakes.
It's also the most comic booky show on TV. They didn't shy away from Grodd. They didn't shy away from Earth 2 or time travel. Stuff like that often never gets properly adapted because of producers thinking audiences won't be on board/able to understand/weirded out/whatever. Flash does it. And does it well.
That said, Arrow has been MUCH better so far this season. I really felt last season was a massive dud, but it has rebounded in a big way. They've got a great scenery chewing villain in Damian Darhk, they've pulled back on some of the oppressive hopelessness that was starting to infect the show (Oliver really seemed like an almost nihilistic character at times last year) while still keeping things a bit darker than Flash, they've gotten the characters back to what works for them (Felicity was terrible last season and though I'm still not sold on the Oliver/Felicity romance, she's at least back to being recognizable), and have introduced some new plot threads that could go interesting places.