I voted for enterprise as the worst trek show. The theme song, the utterly unlikeable captain, unrelateable crew, the utterly, insanely bad writing, the utter inability to grasp trek aesthetics-mechanic coveralls for uniforms, a modified Akira-class model used for the enterprise, naming the ship 'enterprise' at all. And of course, the wierd, out of place, and rather creepy fanservice. I can still remember all of the Sci-Fi channel ads with the Orion girl saying "I'll gladly do what you say" and Naked T'pol etc-really awful, IMO. Speaking of T'Pol, what's up with Brannon Braga taking unemotional, stoic women who by all means should be if anything asexual, and sexing them up? First Seven of Nine (seriously, a Borg?!?) and now a Vulcan? We should count our lucky stars he wasn't in charge during TNG, or Data might have ended up looking like that sexbot from Mass Effect 3.
Well, that's my Least favorite show, Voyager might have been bad Trek IMO, but at least it felt like Trek, Enterprise didn't really have the benefit in my eyes of being able to draw off a pre-established popular trek-era like Voyager did with TNG/DS9, and didn't have the benefit of being good, either.
Well, that's shows, how about movies? Favorite and least favorite? My personal favorite has to be ST VI: The Undiscovered Country. It had a lot to like, memorable villains like Valeris and Chang+his prototype bird of prey, a bunch of different environments such as Rura Penthe, a plot that didn't involve earth being threatened with a doomsday weapon, Someone besides Kirk gettign to pilot a spaceship (Sulu) and a resolution that was semi-uplifting, with the implied coming age of improved cooperation between the Federation and the Klingons. My one and only gripe with the movie was the Mind-Meld Scene with Valeris and Spock-it was very rapey in nature and was very creepy IMO, and left a sour taste in my mouth.
My least favorite would have to be Nemesis. Whiel I really, *really* do not like nuTrek, it takes place almost completely in an alternate dimension, which makes it easier to ignore in my head. Admittedly, they both screwed over the Romulans, one of my favorite factions in the franchise, and nuTrek did it worse-blowing up their homeworld and retconning the rommies into wierd bald, tatooed freaks. Nemesis however, screwed up the Romulans first, and a Romulan Empire blown up in nuTrek is one already completely defanged and humiliated in Nemesis by one of the worst villains I have seen in a movie period, much less in Trek. Not only that, but for a movie supposedly all about the Romulans, it has the Romulans as background characters at best, chumps at worst. It's really hard to take the Romulans seriously after Nemesis, and it not only put the nail in the coffin of the TNG era, but also put a nail in the coffin of what was probably the one remaining TNG era 'villain' faction of any real importance.