Star Trek II: The Wrath of KhanKhan Khan 1982
Possibly the most influential of all the Trek films outside fan circles, Khan is everything people expected a Star Trek movie to be like. It has good effects, solid plot depicting the battle between good versus evil with all the large performances you could hope for without a hint of ham. Bacon sandwiches can be smelt in parts of Ricardo Montalban's performance but never over the line.  Nick Meyer's script and direction are great and from all intents and purposes saved the show from mediocrity.
This is a much better film in every respect to the first film and its a credit that it cost next to nothing (especially since a few FX shots were reused as well as all the sets. The new costumes seem to sideline Trek's established lore regarding Starfleets color coded uniforms (It's harder to predict who's going to die in the teaser when they are all red-Shirts. Spock's death scene is one of the most memorable in the entire series

Star Trek III: The Search for Spock - 1984
Leonard Nimoy's directorial debut may not be the first the most stellar Trek but is a good film nonetheless with all the elements needed to make people happy. Spock was brought back though The ship and Kirk's son both had to go. The galaxy was not in danger but this sort of mission had never been seen before (though later TV Trek would do this all the time).
ST III would mark a turning point in a ST story in that with Spock out of the picture and McCoy out of his mind, Most of William Shatner's scenes are played with Jimmy Doohan, Nichelle Nichols, Walter Koenig and George Takei, the very people he'd been accused of pushing off-screen. For the next few films, they would see larger and larger parts, even with Spock and McCoy back to normal. Compare the scene in Wrath of Khan were McCoy visits Kirk's flat for his birthday and a scene in this episode where Kirk shares a drinks with his command staff sans McCoy and Spock and you see the difference. I mean, we all like to think this is a tight knit crew but as several scenes in The Motion Picture show, Kirk, Spock and McCoy hadn't had much to do with each other or any of their former crewmates.
The first part of the film is sombre as the Enterprise limps home apparently directly after the end of the previous movie with most of the crew reassigned en-route. Of course, demands for a story tend to see continuity rewritten often- Last film added a neutral zone between the Klingons and the Federation (though there's no reason to call this a lapse), this one sort of omits certain details when recalling the events of the previous film and thankfully, although Wrath of Khan was made as a one-off sequel, it contained enough onformation to make Spock's resurrection plausible.
The camaraderie between the crew (Wow Jimmy Doohan is a good actor) and the sense of hope keep this film together. ST films for a lot time had a curse on the odd-numbered films and lucky streak on the even-numbered entries, of course, When 1, 5 and 7 were so disappointing in one way or another, this film often got lumped with them, otherwise the jokes wouldn't be very funny.
Saavik. Robin Curtis doesn't cut it, I'm afraid. She's more wooden than the Santa Maria and her staccato speech just makes Kirsty Alley and Kim Catrall's performances in what's basically the same role stand out so much more. Of course, Christopher Lloyd's Kruge has proven more important to the series than may have appeared at the time when he was supposed to be a baddie for this film. Klingons in the original series had been portrayed like Japanese Soldiers from WWII- Ruthless, efficient and seeking glory but despite from here on in, most Klingons are a cross between Samurai, pro wrestlers and drunken pirates

Star Trek IV: The Voyage Home - 1986
This was the biggest legitimate hit. That means it wasn't wave after wave of Trekkers going to see this several times but also a great number of casual movie-goers. It was also the last movie to premiere without first run episodes airing at the same time (see ST:V)

Star Trek V: The Final Frontier - 1989
William Shatner directed. He came up with an ambitious storyline that no one managed to convince Shatner wasn't a good idea. It's all water under the bridge since
an even worse Trek film was made five years later. But anyway, it's the search for God and guess what, we don't find him. The idea was to keep the story a light-hearted adventure in the vein of the previous film that was a huge crossover hit (ie a lot of people who never paid much attention to Trek saw it). That was the intention. But that wasn't the result. William Shatner is capable of doing decent SF- The Tek War telemovies mostly prove that
 

Star Trek VI: The Undiscovered Country - 1991
This film has perhaps the most complex, yet logical plot since II and Nick Meyer's script also managed the feat of keeping the fun of Voyage Home AND the drama of Wrath of Khan without the silliness of Final Frontier. It's an allegory of the collapse of the Soviet Union at the same time but it's also pure Star Trek and even manages to edjuct some of the perceived cast imbalances of times past. Every one of the supporting cast gets to contribute solutions to the problems without the rather poor attempts to thresh them out their roles in Final Frontier in particular
 

Star Trek: Generations- 1994
Now this is the last film to date to follow the odd-numbered curse and the problem is a very simple one. The entire thing was put together as a marketing dream come true. And it wasn't the best idea to try and link the two Generations in this way. Basically the events in this film give new meaning to convoluted, taking all the worst elements of Star Trek V and ending up with a mess. I hated this film the first time I saw it. I never bought it on VHS when I had bought every previous film as soon as they were released (Finances were tight at that point and buying a bad film wasn't on the cards). I finally got the Region 1 DVD version (mainly because it came as a set with its two successors). In the 6 years since it's release, I had only seen it three times compared to about half a dozen for the film before and after it. But I didn't mind it so much the third time. It's still very mediocre, feeling like a TV two parter (apart from the saucer crash). As mentioned on the TNG page, All Good Things would have made a much better feature film than this- the rationale being that was it had too much continuity baggage  for movie audiences. Lursa and B'etor and Guinan, Picard's brother and nephew and Data's emotion chip arc (even mentioning Farpoint) show that to be 'illogical.'
The nexus is the worst offender. Since the gap between eras was so great, some form of Time-Travel had to be involved and since the script only needed a mcguffin to bring the Captains together though in the end the action isn't big enough (though the threat is) to need two Captains. The problem is the same Star Trek V where sthe films basic idea shouldn't have made it past the initial one-page outline.

Nice scenes- The opening with a rather catty Scotty, Kirk and McCoy and the final scenes of the crew searching through the wreckage.
One thing has to be mentioned. Both the direction and editing are very average. David Carson was a very experienced Trek director but uses some very cliched setups (the worst offender being the tacky zoom-ins on Lursa and B'etor when their ship explodes and the same hack later one for Soren. It looked terrible in Doctor Who and it looks even worse on a feature film. The editing is totally lifeless, especially in action sequences, made worse by the strange pacing which seemed to alternate with Picard sitting on a rock while his ship was engaged in battle. The lighting on the Enterprise D is incredibly dark, almost as if Starfleet couldn't pay the power bill and was cut out, but it was very pretty. Still, it is a film and I suppose everyone was looking to get away fom the look of the series.
It's also the first Trek film where technobabble was used so extensively and how jarring it is to see Scotty trying to wrestle with nonsense in his script. After TNG made an art of speaking total bollocks, this is the moment when you realise how utterly stupid is is and how sloppy the scripting is when you need to write tech tech tech in the script and hope the scientific advisor will make up something believable.
 
 

Star Trek: First Contact- 1996
First Contact really was one of the best films of 1996. So the Trek film franchise had a built in audience that went to see the films in droves opening weekend whether they were good or not (And Generations wasn't), First Contact was a film a lot of non-trekkers would have loved if they had given it a chance. The film was a hit but not in the StarWars sense.
Anyway, action film not in the sense of Star Wars with vast battles, though there is a big Space battle in the beginning, it perhaps could have been made into a TV movie too easily which may have hurt its ambitions against the Lethal Weapon type of pap.
 

Star Trek: Insurrection-1998
The joke is. Odds are bad, Evens are good. The third film wasn't as good as II but was no where near as dull as I, misjudged as V or god-awful as Generations. Insurrection is thje first odd numbered film since Search for Spock that is a good film. Neither of these anomalous good odd-numbered films is as good as any even-numbered entry (First Contact was pretty good), but Insurrection is a good film.
It has problems. The Baku are great and the Sona are a bit silly, especially with all the skin-stretching going a bit over the top. Keeping with odd/even schism in Trek films, the 'odds' tend to have more mythic, more philosophical, almost magical concepts (Machines searching for the meaning of life, reincarnation, the search for God, and a place where dreams come true).
The techno babble is kept to a minimum though its still intrusive when it does rear its ugly head. Even though First Contact and Insurrection were both directed by Frakes, the Enterprise E here looks terrible. The lighting shows how tacky the new bridge is, making the bridge in Galaxy Quest less of a joke.
There is a problem involving the chronology of this movie. As far as Paramount is concerned, one season is one year and if a movie is released in November 1998, the Stardate is 300 odd years in the future. So, the events of Insurrection are supposedly taking place during the height of the Dominion War. It's pretty frivolous for the flagship (there's no reason to assume the Enterprise E is still the flagship but bear with me) to be transporting delegates during the height of the Dominion War. A small mention is made of the Federation's difficulties with Borg and Dominion attacks but that is totally downplayed. Of course, during seasons 6 and 7 of DS9, there were episodes that made little mention of the war but still. I liked Insurrection as it was but DS9 had laid the framework for another action movie with Picard and Co taking on the Dominion. A lost oppurtunity and one Paramount may well kick themselves as they try to scramble with action ideas in the future