I'm no fan of the various Trek flavours (I find the moralising self righteousness too annoying for words).
Have to grant you that. Especially TNG had what I call 'the final five minutes' in which they rammed the moral of the story down your throat. I tend to skip when the plot was clear. In later seasons it was better and DS9 was a bit darker (and the least favorite
Actually I am a book trekkie, I prefer the books which have much better plots, less moralizing and more artistic freedom. Especially the DS9 books turned out some good stuff. 'The 34rd rule' and 'A stitch in time' are very good - If you like to read books,
I can recommend them. Oh, and the two audiobooks 'Spock vs. Q' are great, hilarious actually (they are performed live by Leonard Nimoy and John DeLancie).
Of the original series I like some of the scenery, sometimes (unintended) eerie and unheimlich.