Paramount
Of the 13 extant "Star Trek" feature films, it's widely agreed that Nicholas Meyer's 1982 sequel "Star Trek II: The Wrath of Khan" is the best one. Many Trekkies like the outsize character of Khan and Ricardo Montalbán's equally enlarged performance, as well as the film's exciting, climactic ship-to-ship combat sequence. To remind readers, "Khan" climaxes when the eponymous character hijacks a Starfleet vessel called the U.S.S. Reliant and uses it to fight Admiral Kirk (William Shatner), who's aboard the U.S.S. Enterprise. Kirk, you see, had left Khan behind on the planet Ceti Alpha V in the original series episode "Space Seed," unaware that an environmental cataclysm had turned the entire planet into a desert wasteland. Khan barely survived, and when he finally escaped Ceti Alpha V, he thought only of revenge.
"The Wrath of Khan," which features a story credited to Harve Bennett and Jack B. Sowards (who's also credited for writing the script), deals thematically with facing consequences. Kirk has previously been a forthright but reckless captain who rarely dealt with the fallout of his actions. "The Wrath of Khan" not only has him facing a forgotten foe, but also learning he had an adult son (Merritt Butrick) whom he has never met. It's all about growing up and re-evaluating one's life. Then, at the end, Spock (Leonard Nimoy) dies, showing that there will always be consequences. Youth will not last forever, and one can never outrun their past.
Bennett wasn't just a story writer on "The Wrath of Khan," but also a "Star Trek" producer who was brought into the franchise in 1980 after the financial disappointment of "Star Trek: The Motion Picture." He would stay on to produce several more films in the franchise after that.
In 2010, Bennett was being interviewed by StarTrek.com when, naturally, he was asked which of his "Star Trek" movies he liked the best. Perhaps naturally, he said it was "The Wrath of Khan."
Harve Bennett liked The Wrath of Khan the best
Paramount
It's worth noting that Leonard Nimoy's 1986 film "Star Trek IV: The Voyage Home" was, by a wide margin, the most financially successful "Star Trek" movie, at least until the release of J.J. Abrams' "Star Trek" in 2009. Bennett, a producer, was instantly tempted to call "Voyage Home" his favorite merely for that reason. But then, after a moment's thought, he had to admit that he, along with most of the world's Trekkies, preferred "Wrath of Khan." In his own words:
"My instinct is to say, 'You bet, IV is my favorite,' but then I have to stop and say that I love 'IV,' but 'II' will always have a special place in my heart for the reasons we discussed and more."
Bennett wasn't a Trekkie when he was hired to work on "The Wrath of Khan," and had to go back and watch every episode of the original series to prepare. The episode "Space Seed," he explained in the StarTrek.com interview, spoke to him and left him wondering what Khan would look like 25 years after those events. Interestingly, it took a non-Trekkie to create the story for one of the most beloved "Star Trek" movies ever.
But then, Bennett had more to say about "The Voyage Home," as it too had a novel concept. That is the film wherein the Enterprise crew, having hijacked a Klingon ship they re-Christened the Bounty in "Star Trek III: The Search for Spock," travels back in time to the year 1986 to retrieve a pair of humpback whales. It seems a mysterious, all-powerful space probe back in the future is emptying Earth's oceans looking for a few humpback whales, and the planet is screw since humanity hunted whales to extinction centuries earlier. Bennett also liked that movie, as did most filmgoers.
Bennett still enjoyed The Voyage Home, though
Paramount
As noted above, "Star Trek: The Motion Picture" was a commercial disappointment, so a new creative team (sans "Star Trek" creator Gene Roddenberry) was brought on for the sequels. Bennett, a newbie, struck gold with his "Wrath of Khan" idea, but it was something of a risk at the time. If "Wrath of Khan" had flopped, it could've been the final "Star Trek" film. Luckily, both that movie and "The Search for Spock" did well, and, in Bennett's words, "By the time we got to 'IV' we were confident." Bennett felt that the film's time travel plot was a great way to appeal to a broader audience beyond Trekkies.
It worked. Bennett loved the film, and loved that everyone saw it. "Wrath of Khan" may have been his favorite, but "Voyage Home" got more verbiage from the producer. As he put it:
"Going back to the present created something that nothing else could have done, which is it presented 'Star Trek' to a non-'Trek' audience. All you have to do is remember those scenes in the San Francisco streets. People didn't relate to the characters as 'Star Trek' stars, but kind of as another San Francisco crazy. I adore the lady reacting to Chekov when he asks her 'Where can I find the nuclear wessels? 'That whole scene presented 'Star Trek' contemporaneously to people who'd never heard of it. That's why it was the biggest hit and in many ways the most popular of the ones I did."
The "nuclear wessels" reference comes from Chekov (Walter Koenig) seeking nuclear power for his spacecraft, but having no idea as to where he can get it. He knows nuclear-powered seacraft have what he needs, but he doesn't know where they are. So, he merely begins asking people passing by (including an extra who only got the part because the film's production had towed her car), in a Russian accent, where he might find "nuclear wessels." In 1986, during the Cold War, this was particularly funny.