TOS was a great 2 and a half years of shows : It had a bit of everything - sci-fi, action, drama, cerebral, conflict. It had great episodes , it had bad. On the whole, it was, and still is, watchable as family entertainment. It highlighted issues of the day that were, and mostly still are, relevant. It showed a hope for our continued existence as a species when in all probability we're probably going to wipe ourselves out in a flash of nuclear fire. Or worse.
Character interactions were both militaristic, yet also a family. Kirk was brash, hot-headed and knew when to apply or disregard the rules, tempered by Spock who grew vastly (discounting the laughing version in the original un-aired pilot) during the run : starting off as a stick-in-the-mud by-the-book "man" and later becoming more "relaxed" and (for a Vulcan) jocular. Bones McCoy was gruff, acerbic, and my kinda guy ^_^. Hated failure and death, but often provided keen insight into Spock, Kirk and himself. Sulu seemed almost flighty (pun intended) at times - a new hobby every week, but when the chips were down, and fast action was needed, he was the man to do the job. Uhura, although the concept might seem dated now, was a ground-breaking character for the time : A black woman, on the bridge, in a position of command? Checkov didn't appear until part-way through season 2, but quickly settled in, to be the young boy of the family,. He had some good episodes written for him. Scotty was Scotty was Scotty. Loud, hard-head, ultra-dependable. Good man to have at your back.
TNG : Didn't really get "good" until half-way through Season4, IMO. First season was actually terrible. Wesley was an ultra-annoying version of Checkov, and generally just came across as someone needing a baseball bat to the head. Picard was calm, almost cold, very controlled. Riker....seemed almost as changeable as Sulu - one episode dry and calm, the next a womaniser, the next a hot-head. Data grew as a character too, in line with his oft-stated goal of "becoming more human", but he did have his off-days. Deanna Troi ... irked me for some reason...must be the voice, because the curves certainly weren't displeasing :P Speaking of voices - Crusher's temporary replacement, Pulaski, has always annoyed the s**t out of me, no matter what she was in :-\ Crusher herself was amusing, but no McCoy. She tended to be very flighty and skitterish but did the job when needed.
DS9 - Never really got into this version of the show - space station. how dull. Then they threw in a bone of a ship, Defiant, which got destroyed 2 or 3 times...just....mediocre all the way through. Especially with the religion and Dominion War aspects. Can you believe they wrote a whole season for a holo-character??? He was better off in The Time Tunnel :-\
Voyager - laughably awful. It's almost like the writers had given up with DS9 and were just going through the motions for most of its seven year run. Kes was a cute little thing that had some good stories and episodes. And as for Janeway, I've always had a thing for Katherine Hepburn, so she was a win for me ^_^. Seven of Nine with her Borg-implant enhanced bazooka boobs added a little colour in the vein of Spock and Data exploring humanity, but she just was bland otherwise. Paris and Kim and Neelix and Chakotay and Tuvok and B'elanna seemed to be clay all through the run : becoming what was needed in each episode, then reset for the next. Yet another whole season dedicated to holo-characters - or in this case, a whole town of them :-\ Still, it was more fun than the dour, grey, dull DS9.
Enterprise - Makes you wonder why they even bothered. It just never started to live up to what was claimed for it. Changed it's ethos too many times. Re-wrote a lot of back-history from the other shows. Alien Nazis, world-destroying probes, interfering and rude vulcans. blandness all the way through. I kept waiting for Archer to say "Oh boy. Why haven't I leaped, Al?" The rest of the crew seemed very disinteresting too. Crap, crap, crap.