My favorite 'Star Trek: The Next Generation' episode is "Darmok". Communication and cooperation under extremely difficult situations and cir
stances. Paul Winfield, an amazing actor by any account, was brilliant as Captain Dathon. (
I once used this episode as a Case Study in a business management class; got high marks for it.)
I'm far more of a Trekker than a Trekie. I think I was too young to get the original series when it first aired. Even after trying to revisit it later I just couldn't get into it though I respected it for what it was and meant for the times. Picard is much more my type of captain: cerebral, ethical (most of the time), and more level-headed. He wasn't a skirt-chaser (most of the time). I also think Patrick Stewart is a much better actor -- I know this will generate some fuss; just a personal thing, I suppose.
I can't say that I have a favorite 'Deep Space Nine' episode. There were some I liked and some I didn't. I did watch it, and re-watch it, but I think one of my problems with it was/is that the action generally has to come to them and some of the characters feel stereotyped or generalized.
I do like 'Voyager' -- I'd put it second to ST:TNG -- but, again, can't really cite a favorite episode. I did have problems with the show when they had Janeway start to go all angry (slightly crazy?).
As for "Enterprise' -- I give it a C- to a C. Although I've been rewatching it, it still is too much of a mish-mash and very white testosterone. And that theme song!? Ugh.
I blame Brannon Braga and UPN executives for ruining the franchise for me. Both had a level of misogyny and homophobia, discounted/ignored canon, and -- in the end -- I think looked more to bottom-line-return than to fan-base.