Nemesis. I agree with the OP that it was boring. A clone of Picard becoming Praetor of the Romulan Empire caused my suspension of disbelief to snap. Data's death seemed unnecessary, and having B4 there as a built-in reset made Data's death feel hollow. The ending was melancholy and wistful, when it should have ended on an optimistic note.
All in all, if the storyline were tweaked a little, it could have been a better movie somewhere in the middle of TNG's film run, but it was awful as a sendoff.