The First Trek movie was trying to be something bigger than what it was, and ended up failing from it’s own pomposity.
Wrath of Khan brought the movies back to their roots, with focus on adventure and the characters. All things considered, the stakes were really not that high, Khan may have had the Genesis device, but really the movie was about his personal vendetta against Kirk.
The Search for Spock was essentially trying to undo the ending of the previous story. The addition of the Vulcan mysticism was a bit of a hand wave and kind of flew in the face of what was known about Vulcans.
The Voyage Home had the biggest stakes of the original quartet of movies with the Earth in danger of destruction, but it was mostly just a fun caper with the cast playing the fish out of water in then Modern Day San Francisco.
The Final Frontier had not only the first movie’s problem of trying to tell an epic story line bigger than anything they had ever done before, they also got saddled with a first time director with some clear ego issues.
The Undiscovered Country may not be the most beloved of the original movies, but I’d say it’s the one that got it right. It had an epic story line of the Federation and the Klingon Empire settling their differences, and those conspirators who were trying to stop it. Yet it was still a very character driven story with the crew dealing with conspiracies aboard ship and the Kirk and McCoy trying to survive the prison planet.
Generations was a bit of a failure largely due to it being another epic story with far too much going on. And the Enterprise D crew found itself in the same position as the original crew, or not really having their footing with regards to the movies.
First Contact is the most popular of the Next Gen movies, and it has it’s moments, but the focus on Picard’s suddenly developed Ahab complex regarding the Borg was kind of out of character for him. Furthermore, the introduction of the Borg Queen was the first step that lead to the downfall of the Borg as a credible threat in the Voyager era.
Insurrection should have been a home run, it had all of the elements that would have made a good episode of the series, but spread out on the big screen it was not enough and ended up rather boring.
Nemesis with it’s Picard clones, Federation Dune Buggies and Data’s idiot brother was just sad.
I have yet to really get into New Formula Trek. The first movie felt too much like an attempt to throw every possible trope from the series up on the big screen. It felt less like Star Trek than like Galaxy Quest: The Serious Movie