Jerry Goldsmith = sucks (I put it into an equation).
Look, I don't venerate Goldsmith the way some people here do - specifically the ones who think his later Trek scores (with or without co-credit to his son) are TMP's virtual equal - but he gets lifetime Top of the Heap status from me on the basis of Planet of the Apes and Patton alone.
Do you also think his music for Alien sucks? (Occasionally I can hear a point of contact between his scores for TMP and Alien, which it can be presumed were written more or less simultaneously.)
Someone ought to retitle this thread. The real "best Star Trek composers" were the ones who wrote for real Star Trek - that is, the TV series. Many TV series of that era had music with some punch to it, up through the early '70s certainly (Columbo, for example). You know - music that called attention to itself while serving the story at the same time, music with character. This is the milieu that Goldsmith worked in for years (as did many of his contemporaries best known today for their Trek work, such as Gerald Fried and Fred Steiner).
So why precisely does Mr. Goldsmith (or at least the Goldsmith of TMP) suck? Can you get specific? I myself heaped scorn on Leonard Rosenman's TVH score on another thread, but at least attempted to give a musical example or two.
I am strictly going by their work on Star Trek. I believe TUC had the best score.