Here's an ignorant question; how sure can we be about writing credits? It seems to me that the actual credits can differ greatly from the official credits for writing - screenplays or teleplays is what I'm referring to. The City On The Edge Of Forever is an obvious example.
Also, was Gene Roddenberry's work ever 'touched-up' by others, such as Dorothy Fontana? These kind of questions muddy my opinion of his writing ability - I just don't know enough about it. He might have been great, good, fair, or poor; it kind of depends on how much was his, and how much was not.
On many shows, the executive producer is the one who does the final draft on all the scripts, usually without credit. However, we do know that the final draft of "City on the Edge" was Fontana's, after Roddenberry had taken several passes at it. So it must've varied case by case.
And even when a credit is his alone, there have been rumors about a ghost writer, The Motion Picture novelization as an example.
Completely false, long-discredited rumors. The claim was that Alan Dean Foster had ghostwritten the TMP novelization, and this came about for two reasons: One, confusion with the Star Wars
novelization from two years earlier, which Foster had ghostwritten under George Lucas's name; and two, an overseas translation (French, I think) that mistakenly lopped off the latter 2/3 of the writing credits (screen story by Alan Dean Foster, screenplay by Harold Livingston, novelization by Gene Roddenberry) and thus gave the impression that Foster was the author of the novel.
But to anyone who's at all familiar with Foster's style, it's obvious that he didn't write the TMP novel. That novel's prose style is awkward, clumsy, just as you'd expect from the debut novel of a screenwriter who'd never worked in prose before. It has stylistic traits that resemble screenwriting practice, like using italics heavily to emphasize actions and descriptions (just as important stage directions are often underlined in scripts). And it reflects Roddenberry's well-known preoccupations (futurism and sex).