I'd agree with that, 86 is weakest, 83 is best, but they're all great.I'm currently watching Deutschland 86.
Watched 83 a while ago and enjoyed it. My Germanic friend tells me that 86 is the weakest of the three, but 89 is good. I'm quite liking 86 so far, so if 89 is better, then great. It is interesting seeing all this Cold War stuff from a German perspective.