I probably have...fairly popular opinions on this, but:

• The Motion Picture. Crap film. It's the script for a TV episode, goatse'd out to an over two-hour run time. The pacing is just tectonic and it's just way up its distended ass. A large part of the problem is the movie basically didn't get edited; most of what they shot ended up in the final cut. You could improve it a lot by paring it down.
• The Wrath of Kahn. Very good movie; I think it's the closest to the franchise comes to being a classic. Some serious themes, exciting battles, a very good soundtrack, some really awesome hairdos, KAAAAAAHN!, some bagpipes...Probably the best of the movies to date.
• The Search For Spock. A decent movie. If you subscribe to the "odd numbered Trek movies are bad," this is the best of the odd movies. It's not as exciting or tense or well paced as Wrath of Kahn but it's still competent. Worth a watch.
• The Voyage Home. The obligatory "travel to the present day at time of filming" episode of the original series movie era. It's got a quirky and weird plot with a somewhat anvilicious environmentalist message, but it's such great quality time with the characters, and it has such a wonderful soundtrack. Wrath of Kahn I think officially tops it but Voyage Home is so fun that it's my personal favorite.
• The Final Frontier. I think you can fix the Motion Picture, but I don't think you can fix The Final Frontier. The plot doesn't work. Did they actually shoot God to death? What...was all that? Fortunately nothing of importance is established here and you can safely just skip it.
• The Undiscovered Country. I rank this one about on par with Search for Spock; it's competent but not spectacular; it's got too much of "it's the last original series movie you guys" in it. As Mr. Plinkett said 'Then they pose for a picture that no one took.'
• Generations. It's as good as it is stupid. The executives didn't have faith that the TNG crew could carry a feature film, so they had to contrive a way to have Kirk involved, and the plot they came up with required the villain and the protagonists to do exceptionally stupid things. With that flaw in place, they executed it about as well as they could.
• First Contact. Dumb action movie. Instead of having any Star Trek in it, it's got violence and body horror and swearing. If you want to see Die Hard, go watch Die Hard, because Die Hard is better.
• Insurrection. This one comes the closest in terms of plot, tone and production value to the TV series. It really does feel like an episode of TNG...Oh no. Remember Season 7's Journey's End? Where the Enterprise is sent to force some Native Americans off their land because reasons? And Picard was going to go through with it until Wesley blew it up? Yeah turns out Picard would have sided with the natives if they were white. I mean at least Troi's boobs are starting to firm up.
• Nemesis. "What if we cram The Wrath of Kahn and First Contact together? Big dumb action movie with an asshole bent on revenge against the captain out of nowhere, and we kill off the main cast member we could most plausibly revive later?"
• Star Trek (2009). Lots of trekkies have made mediocre fanfics of dubious quality over the decades, and among them is one J. J. Abrams. And I guess it was fun; we got to see Bones give Kirk shots he didn't want, we got to see Scotty babble about how the engines can't take it, we got to see Chekov fail to say the letter V, we got to see Sulu leave the parking brake on, we got to see Uhura wear a very, very short dress, we got to see Kirk bang a green chick...and I guess that's enough. And that's where I abandoned the franchise.