Im surprised so many people rate The Voyage Home so high and TMP so low. They are the complete opposites of Trek, one a topical comedy the other a true Sci-Fi film. That being said here is my list:
1. First Contact (a slight edge over number 2)
2. Wrath of Khan
7. Undiscovered Country
Stark trek 11, still kind of the fence about the Star Wars plot. As a side none of the movies are entirely unwatchable (kind of like Bond), but the last two get viewed the least.