TOS rocks. Duh.
TAS I haven't watched yet.
TNG rocks, and it got better with every season.
DS9 is an awesome TV series, not just a ST or SF one. It also got better and better as it progressed. (Bajoran religion stuff was often boring tho'.) If you watched it end to end and didn't like it, to each our own. If you only saw some season 1 episodes and decided it sucked 'cause they're stuck in a space station, you're wrong and you're missing out.
VOY mostly sucks. Should have been even grittier than DS9 to make sense, but they went for tried and foolish for the most part. I disliked most of the regulars. Picardo is excellent. Tim Russ was great - maybe not Oscar material, but he did a very good job with portraying the first long-run full-Vulcan in the franchise. Ryan, minus some awkward moments, was way better than Lien (speaking of whom, what's with the lisp?!? Do folks all talk like her wherever she hails from?). Ethan Phillips proved himself much less annoying than his Neelix character. Robert Beltran/Chakotay was OK. Roxann Dawson/B'Elanna Torres was a little underdimentional acting-wise, but also underutilised, what with her pregnancy or some other reason. I fiercely loathed Robert Duncan McNeill and Garrett Wang, their bridge officer characters and their singsong delivery: high-low, aye captain, on screen, shields up. Ugh. Finally, Mulgrew and her character, whoever wrote it the way it was. On a bad day, and there were scores of them, she deserved nothing less than being stranded with angry natives, or at least one or two keelhauls with an old spacesuit on; on an average one, I'd have welcomed seeing her receive a (half-)Klingon headbutt each time she went into hissy murmur, preachy mode...
ENT is good. There, I said it. Season 2 was a little dull. IMO the Xindi arc is best consumed in a binge-watch, as I did (enjoyed it a lot). Season 4 is solid. Oh, and as for the theme song, the verse is even good compared to the chorus, which blows.
On to movies. Liked all, except The Final Frontier (obviously), Generations, Insurrection (basically a double-length bad TNG episode) and Nemesis.
Speaking of unrelated sci-fi movies, the Abrams Trek trilogy is crap.