I love all the shows, the I like Arrow the least. That said, the 2nd half of this season was a huge return to form.
I say 2nd half because people seem to forget that the first part of this season was dealing with that dumb drug dealer guy that no one remembers.
As far as finales go, yup Arrow took the cake. The return of Slade, the sacrifice of Malcolm (actor isn't returning), and just all of the character moments were great.
The "cliffhanger" was a bit meh, since obviously they're not killing off most of those people. They didn't really need it either since the whole choice element beforehand was good enough. Despite that, terrific finale, Slade and Oliver are a great combination that I missed, and Adrian has been a terrific villain.
I hope they don't pull a Flashpoint thing with Flash next season though, where everything is resolved in the first episode. Just feels like such a huge emotional move, only to reset so quickly, but at the same time, I doubt they have the balls to leave him in the speed force for long.
Supergirl...........it was fine. Seemed a bit forced at the end though. Good lead in to the next season though, curious who that is.
And Legends is great. The first season was really hard to watch and I was about give up, but most of the 2nd season really cleaned up. They found that great balance between good character moments and over the top cheese, and embraced them both. So I'm looking forward to all of them returning.
Edit: On 2nd thought, I think maybe it would be a cool idea to end Arrow on the cliffhanger. And then maybe in a year or so, or at the end of the next season of The Flash, have them show Oliver as a broken man who really did lose everyone on the island.