I've got fond memories of TOS, even though most of the episodes were, i retrospect, pretty awful. The only one which sticks in my memory as being any good was
Errand of Mercy – it's the only one I can think of where the Federation actually found an alien race they could learn from, rather than teach... An awful lot of the episodes seemed to be along the lines of
ALIEN: "Hi there, humans! We live in a paradise."
KIRK: "Aha! But your paradise is artificial! Here, we'll turn it off for you. There ya go!"
ALIEN: "Augh!"
KIRK: "Suffering is good for you. Buy more hamburgers. And away!"
(roll credits)
TNG was awfully group-huggy. It did have its moments, mostly after Roddenberry died, it has to be said, but what with all the stupid holodeck stories and the unremittingly beige decor, it did get very wearing.
I actually liked DS9, myself, even though it was a ripoff of the (vastly superior) Babylon 5. The static location seemed to allow for more in-depth exploration of some of the alien races. And they must get bonus points for going back in time and farting about inside the "Trouble with Tribbles" TOS episode.
Voyager... oh dear. Oh dear oh dear oh dear. Oh dear oh dear oh dear oh dear oh dear.
Threshold: says it all, really. "There's no small irony in the fact that an episode that so badly mangles evolution manages to be the single best argument against a loving God."
Enterprise could have been good, I think (especially if Paramount had stuck with the original idea of calling the captain Jeffrey Archer... comedy gold, at least in the UK). But all the time-travel junk was just a dead weight around the series' neck. And the opportunity to show humanity learning and developing was dumped in favour of pointing out to the Vulcans where they'd got it wrong all the time.
As to the new film: I hope it doesn't crash badly, because I want to see more SF made for TV and the big screen. If it is a flop, it might put the studios off. Personally I'd prefer something other than Trek, though. The new Battlestar Galactica has shown that it's possible to make a decent grown-up SF drama series; Stargate SG-1 showed you could make decent SF brain-candy with a sense of humour; and Dr Who proves that you can make a good SF kids'/"family entertainment" show, too.