between these two Trek movies of ones w/ the original series cast, The Motion Picture and The Final Frontier often stand out as the worst two...and it's because compared to the rest of the group, they don't really fit in. 2 (The Wrath of Khan), 3 (The Search for Spock) and 4 (The Voyage Home) were all part of one story arc (the "Genesis Trilogy"), and 6 (The Undiscovered Country) sort of continued those themes.

But let's look at the other two:

The Motion Picture:
-Completely different uniform style
-More focus on characters that would never be mentioned again
-A threat that happens, never mentioned again

The Final Frontier:
-Characters acting differently (like turning on Kirk, when they immediately went to his side in The Search for Spock)
-Starfleet heads being useless
-Enterprise A being a mess (Sure it could be explained that it was because it was an old ship rechristened, but whatever)

There's other factors, but yeah...neither movie fits the rest of the original Trek movies tones, and could easily be ignored. Which one do you think is easier to mentally wipe from canon though?

Number one was originally conceived as a pilot to a New Generation Star Trek TV series, hence the new characters.

Number 5 is a film I cannot sit through, no matter how many times it has been on TV.

#5 is really a REST LEAVE movie.... It isnt meant to be like the others!!

Kicks gotta rest sometime right?