Honestly I loved certain aspects of Kylo Ren very much. The movie was almost a carbon copy of Episode 4, but I like how they twisted him a bit. He's being "seduced" by the light. He's being torn apart in a different way, and I liked the approach. The rest of the movie was almost too direct a clone of the original, but I think his arc will be just as good or better than Vader's. I know you weren't getting at where he might go, just what we saw, but I think it was a good setup.
That said, I think Vader had some humanity at various points in the OT. His anger at Obi Wan was human. He perceived wrongdoing on Obi Wan's part, and saw their final conflict as a chance to get revenge and prove a point. That's very human, machines don't care about revenge, feelings, anger, or anything like that. In ESB we see a strong element of sadness when he realizes he lost Luke, and that Luke would literally prefer chancing death over accepting who his father was.
In ROTJ obviously, he was very much human and it showed in probably his best storyline of the entire series. He was hurt, subdued physically, faltered, and literally saw him at his most human (and all of this with his mask on). But that's really where he was coming back fully to his human side, so we may or may not want to count that for the sake of this topic.
Kylo Ren is possibly a more interesting character. I will be extremely interested to hear more of his story. How he went from Ben, to falling with Snoke. How he got so twisted in his mind, what would make him turn on his family like that. We know what broke Anakin and turned him into Vader, but we have no idea whatsoever what broke Ben and turned him to Kylo Ren.
Excluding the prequels, we first saw Vader as a ruthless enforcer of the Emperor's will, un-feeling, absolutely un-caring. We saw him (always in the mask) steadily becoming human. We're seeing Kylo at his last seconds of humanity, and will likely see him completely turn into a monster over what he did to his father and the defeat he suffered by a token character that was useless in the story completely, and an entirely un trained force sensitive girl who had literally touched a lightsaber for her first time.
He had a full misunderstanding of what his grandfather would have wanted from the start of ESB on, is completely warped by Snoke and wants to emulate the legend of his grandfather rather than who his grandfather actually was. Now missing two limbs, a face that is scarred deeply, and wounds that will likely require a suit to keep him alive... He'll get his wish, and it will be interesting to see how he deals with turning into something worse than even he imagined his grandfather was.