Sons of anarchy definitely
walking dead I have to disagree with, they completely fukked up something that should of been great in the last 2 minutes of the last season but storyline wise I don't see the problem, it's finally reached the point of the story it's fans have wanted it to and aside from the usual 3 or 4 near pointless/boring episodes each season (which isn't bad for 16) it's been pretty consistent, seasons 5 and 6 (more 6) were great imo.
The wire came very close with the whole serial killer/mcnulty storyline in its last season imo, but luckily it didn't get too ridiculous and there was enough going on elsewhere on the show that saved it.
I'd like to think power won't but it's been given a couple more seasons so who knows.