One of my favorite character arcs in all of literature is that of Spock's, from that stereotyped "rationality" through developing his own comfort with human emotions. Even as from the outside, it seems little has changed, the initial Spock and the final Spock are very different people. Kirk's journey is flashier and easier to find in the story, but far more trite and it's been done a hundred times. I don't know of very many parallels to the Spock arc. I grew up with Star Trek but I find I didn't really "get it" until much later in life. I wish the Original Series wasn't so painful to watch because of its superficial flaws, because while I would not presume to say it's the "best" Star Trek, it probably is the most legitimately "literary" at its best.