Hey hey, I have seen all the Trek movies countless times before except the latest 10th movie, which I haven't yet seen at all.
But I agree that IV and V are the worst movies of the original crew era. TNG era's worst is definitely Insurrection, the ninth movie. My favourites are the second and the sixth from the original crew era and then First Contact from the TNG era.
All the movies special editions from 1 to 8 are currently on sale at a local store, I immediately bought the first two movies, but I'm going to buy all of them as soon as I can.