One example immediately comes to mind: The Final Frontier. Much of the story was so "out there" that Gene Roddenberry himself considered it outside of canon. Spock's long lost half-brother hijacks some ambassadors and steals the Enterprise to go find God. I for one thought the messiah complex idea could have worked quite well if Sybok had been more stoic and detached and had not spent so much time grinning. It would have made the character more menacing. This is only a minor point, however. I feel the missed opportunity here was with the God-creature that was encountered on the planet.

Ultimately, the entire movie ends in an anti-climax with the defeat of a second-rate nasty who can be destroyed by a few blasts from a Klingon disruptor. A simple change would have made a HUGE impact on fans and created a kind of story arc bridging the latest movie with the series' pilot episode. The evil entity should have been Gary Mitchell.

TOS fans will recall that Gary Mitchell was Kirk's friend from his Academy days and Kirk asked for him on his first command. In the pilot episode "Where No Man Has Gone Before," Gary Mitchell developed extraordinary paranormal powers after the Enterprise passed through the great barrier at the rim of the galaxy. Ultimately, he became dangerous and was presumed destroyed. Bringing back Gary Mitchell would have made a great story. It would have made much more sense and created a bit more drama. Would Kirk still be harboring guilt over having to kill his friend? How would he feel about having to do it again? Would this lead to a revelation as to why Spock could not kill his brother? Star Trek V was panned by a lot of fans, many who regarded it the "worst" of the movies, but it had possibilities. The movie was about family, about how important families are in our human experience and how the crew had become a family of sorts. If only for a few key changes, The Final Frontier could have had an impact similar to The Voyage Home.

You can link nearly all the movies with episodic counterparts:

TMP - The Changeling
TWOK - Space Seed
TSFS -
TVH - Tomorrow is Yesterday
TFF - Return to Eden

I - a prolonged and effects-heavy TOS episode, but still with the "freshness" and overall optimism of the old series. I would have easily accepted it as the pilot of the Star Trek II series.

II & III - Although these have fewer and cheaper effects, they rather turn to the usual way (sci-fi) movie stories are told. The atmosphere of TOS is sacrificed for big emotions, hatred and death. An outer sign is the worn-out look of people as well as starships and the dark bridge of the Enterprise.

IV & V - There is not much Trek left in these movies, except for the basic setting and characters. The movies are produced in a way to appeal to the common theater visitor, with crazy stories and funny quotes (and often cheesy acting).

VI - Basically the same as for IV & V, but it was mostly not funny at all. I didn't even recognize many of the characters anymore, so much were they distorted to serve the story.

Back to the possibility to create a story arc, this wouldn't have been possible at the time Star Trek V was produced, considering that it was not very Trek-like anyway.

Regarding ST V, it was only done in by the attempt to add slapstick humor in the wake of the popular, comedic ST IV. These attempts at humor didn't fit at all with the more serious elements. I did like the exploration of the inner demons of the characters. Also the special effects were not by ILM and looked very bad. Finally, the Klingons were poorly done and made zero impact.

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When you're in the Sol system, come visit the Starfleet Museum

I really think Khan is only as memorable as he is because he was featured in the second movie. "Space Seed" was arguably one of the better episodes, but the movie certainly lifted the character out of episodic obscurity. Fans who only vaguely remembered who Khan was learned of his previous encounter with Kirk and the Enterprise by the dialog in the movie. No exposition was really necessary. The really young fans who never heard of Khan could then enjoy watching the episode that started it all with renewed enthusiam. The same effect would be seen by re-introducing the now god-like Gary Mitchell character. Newer fans would seek out the pilot episode to bone up on their Trek history.

You're right in that TMP is very cinematic, it shows much more effect as well as dialog than the TOS episodes, no matter if this was actually missing or not. TMP is "opening the big screen for Star Trek".

The later movies certainly had denser stories, but they obviously suffered from too many people bringing in their particular ideas. I have the impression that it was tried to make Star Trek popular among non-fans, which is very obvious in ST IV and unfortunately opened the way to spoil ST V (whose basic plot was promising).

But this is all academic. Do you have any good ideas for new movies?

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When you're in the Sol system, come visit the Starfleet Museum

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"The things hollow--it goes on forever--and--oh my God!--it's full of stars!" -David Bowman's last transmission back to Earth, 2001: A Space Odyssey

The 359 Webpage

He also was reunited with William Shatner on two nonconsecutive occasions.

God bless the IMDb.