I voted for Nemesis. So many errors, plot holes, and weak elements in it to forgive.
Of the others, I actually quite like Generations though always see it more as a TNG TV Movie than a feature film. First Contact is one of my favourite Trek films ever made. Insurrection is pretty lame, but it at least has some development and makes sense--plus it also gave us the great looking Son'a ships.
Commander Austin Harris, First Officer, Deep Space Nine (by FltCpt. Bossco)
8.01 - Darkest Before Dawn
(Chapter 8 added, 12/09/2015)