Supposedly the bravado that the Kirk character had on the original series came from the fact that Shatner played Alexander the great in a stage play. According to Shatner of course,lol.

Roddenberry said he was typed as "Horatio Hornblower in outer space".

Leonard Rosenman's score for Trek IV is a bit too much like his score for lord of the rings by Bakshi. It borrows heavily from it. The leitmotif of the opening theme is nearly identical.

Horner always borrows from earlier scores he has worked on as well. Even John Williams does it.

Goldsmith generally composed wholly new soundtracks except for reusing Alexander Courage melodies, The title of the motion picture and the theme of the enterprise.

Spock had his own theme in Horner's score for Trek III and trek II. As far as i can tell Capatain Kirk never had his own theme. Nor did most of the characters. It was John Williams in Star Wars who had themes for the different characters. In Star Trek the Enterprise itself had themes written for it.

From what i read the new Score for 2009 tried to have a themic unity and a character theme for kirk. I believe they thought of Williams more than they did Goldsmith, or Horner.

Usually these types of films have a heroic theme or march for the good guys, and an evil theme for the bad guys. Khan for instance had his own theme, and the Kilingons got a theme in the motion picture though there they were not the evil presence in the film.