My opinion is that Insurrection is the least offender of the TNG movies, but most people will disagree. The reason why I prefer it is that it feels more like Star Trek TNG than the other ones. The plot isn't air-tight but it's a masterpiece compared to the other three.
I agree with Jon1701
that the TOS movies are better, though. Hell, even TFF is more entertaining than any of the TNG ones.