I don't think there is a bad Trek score amongst the lot of the Trek movies.
Like others here, I think it would be next to impossible to truly narrow down all the fine choices to a single track. If I were going to try, though, I'd probably cast an additional vote for "The Enterprise" from TMP. Absolutely breathtaking, and a type of cue that would never be written for a movie today, unfortunately.
I'd also like to mention Dennis McCarthy's score for Generations
as one that I think is often under-appreciated. McCarthy sometimes gets a bad rap for his TV work, but that is largely due to the constraints placed on him during the latter half of TNG and beyond. However, if you listen to his early TNG work, it is clear he has a much greater range than the rest of his series work would indicate. With Generations
, where he was allowed to move out of the "sonic wallpaper" box and actually use grand themes and motifs, I think he did an excellent job. He is no Jerry Goldsmith, but I think his work on that film was very good.
Lastly, I'd like to mention James Horner's weaving of the TOS theme into his work. I think he melded the TOS theme with his own cues perhaps better than anyone else. In particular, I always love the first minute or so of the end titles cue from TSFS where he not only quotes the TOS fanfare, but actually the TOS theme itself before going in to his own theme. Very well done.