You're forgetting Gotham... Right now that's probably the best of the lot irrespective of last season.
No offence if you like Gotham, but I omitted it on purpose for two reasons
1) Flash, Arrow and Constantine share a universe and share it well, the Flash/Arrow crossovers have been great and are always great fun to watch.
Not sure if Gotham is in the same universe, and if it is it's set well before Flash or Arrow.
2) While I sometimes enjoy Gotham - or at least enjoy aspects of Gotham, I find Jim Gordon a boring character (which is. a shame as in the Nolan films he was anything but, perhaps that's down to the quality of the actor). Bullock is a more interesting character.
The 2 best things about Gotham, IMO are the Penguin, who's fantastic, and the kid who plays young BW (yes, Alfred is good too, wish we'd see more of him). Otherwise I can kind of take or leave most of the cast - really wasn't impressed with the casting or performance for Harvey Dent, who should be a much more important character.
Also, Gotham is basically an extended prequel -whereas Flash, Arrow etc, are actually the adventures of the characters we know and love ( and as a comment on Arrow, I always hated Green Arrow in the comics, but the tv version is interesting and likeable - particularly in season 4 - and Stephen Amell does a great job. I always thought of Arrow as "Batman with a bow" but the show's made him much more than that, and I particularly like the way it's about his team, rather than just him).
Anyway, I can't watch Gotham without thinking " man, I wish they'd flash forward to show us Bruce as Batman, working with Gordon" and apparently we'll see Batman, in the very last frame of the series. Personally, prequels don't do much for me - Star Wars and Hobbit trilogy I'm looking at you !
But, if you like Gotham I respect your opinion (it's a good show) - I just can't get past the prequel thing .
Cheers.