Hmmmm.... well, I mean, I hate lists and ranking things, but I'll give it a try.
1. TOS. I mean, of course. How could it be anything else?
2. KHAAAN! Still the perfect example of how to make a good Trek movie.
3. TNG. This was actually a hard choice. I want to rank it lower. I went back and re-watched it all a few year ago, and I noticed that while TOS has transcended age to an almost abstract level of plot, because of the simplified sets and use of film (ONE TOOL IN ENGINEERING!), TNG ... well, it feels very very 80s/early 90s. In addition the hit/miss ratio (the number of really, really bad episodes) wasn't great. Still ... I can't forget that:
a. The show brought the franchise back; and
b. How excited I was to see it every week when it aired; and
c. How good the chemistry was between the cast; and
d. How iconic some episodes are.
4. DS9. It started a little slow, like a Babylon 5 ripoff that didn't know what to do. And it's a shame that we don't have a definitive remastered HD version. But this was the best of the new Trek series, in my opinion. I just can't put it above TNG because, well, TNG kick-started the whole thing.
5. Beyond. WOAH! Yeah, I said it. Look, I'm not a big fan of nu-Trek, although I think the casting and chemistry is great. But while the first movie was good, and the second movie ... was, the third movie truly captured the essence of Trek. Does it have problems? Sure, what Trek movie doesn't. But even the goofy parts (ahem, Beastie Boys) felt so very Trek.
6. James Blish adaptations. I grew up reading these (the local library had copies). They were amazing.
7. The Undiscovered Country. The second-best TOS movies is still better than any TNG movie, which brings us to ...
8. First Contact. A solid TNG movie. So much better than the first that, for a brief time, it seemed like the old even/odd rule was in effect. If only.
9. Voyager. The answer to the question- is a mediocre Star Trek series better than no Trek and better than most Trek movies? The answer is yes. There was a lot of good stuff in this series (I loved Janeway as the Captain) but it just never resonated.
10. The Motion Picture. So ..... very ..... slow ....... such ..... weird ..... set design. Still, pretty good Trek.
11. Trek 2009. Great cast, fun story.
12. TAS. Animation is terrible. Decent for kids. Good plots, considering. GREAT for memes.
13. ST: DISCO! The jury is still out on this one. It could move up substantially, or down.
14. The Orville. Yeah, it's total Star Trek fanfic with a high budget and questionable humor. Go in with low expectations, and be pleasantly surprised.
15. Enterprise. So, here's the thing. Theme song? Terrible. First season? Meandering (friggin' temporal war?????). But then they really kicked it up a notch, and it became good. Why didn't I rank it higher? Because it had, arguably, the worst finale outside of Dexter. It was like the series creators felt like taking all the fans that loyally stuck with the show until it got good, and then PUNCHING THEM IN THE FACE. Yeah, I'm still angry.
16. Into Darkness. Um, no. I mean, it was fun, kinda. I didn't hate it.
17. The Voyage Home. Fine. Fun.
18. The Search for Spock. This is the last of the watchable. It's perfectly cromulent.
19-22. PLEASE GOUGE OUT MY EYES. The Final Frontier, Generations, Insurrection, Nemesis. All of these "movies" are just exercises in masochism. You will never get this time back. Even if there is a temporal war.