My partner and I are going through the films(he has never seen them before)and guess what his favourite is so far?
He LOVED TMP!!!!
He said he LOVED the '70's SF design aesthetic and the grand story and the evolved humanity theme. I showed him TWoK and said, "If you felt that way about TMP, you're going to LOVE this one...." and guess what?
He finished it and said, "What was all the fuss about? Why do people label TWoK as this GREAT movie?!? TMP was a MUCH better movie!"
So, there ya go.
I watched all the Trek films with my ex a while back as she had never seen them (had never seen any Trek actually) so over the course of a weekend we watched five of the six TOS films and she pretty much had the same reaction to Kahn and the thought that of the five we watched, Search for Spock was the best.
Personally I like all the films apart from Final Frontier, they all have little scenes or moments that I really like (I'll probably regret saying this, but I'll defy anyone to not think that when Enterprise in Nemesis warps away from Romulus and literally spins over just before the jump isn't a cool piece of FX) but my favourite has to be The Undiscovered Country of the ten.