Best thing are the ship designs. Love 'em.
My favorite are the movies, primarily ST II and the Director's Cut TMP: the characters are well done, the ships had a much more realistic feel than any ther period, and the technobabble was kept to a minimum. I love the movies, the rest I just like...
I like TNG okay, more because it was the only decent sci-fi at the time. The frist two seasons were dogs, with a few gems in them, but it improved rapidly through the rest of the series, once the characters were established.
TOS: Okay -- but it's bad. Really bad. If it werent for the fact it blew the doors off the otehr sci-fi of the time, I'd never have watched it. Can't watch much of it now.
DS9: beginnng to wish I'd stuck it out a season or two.
Voyager: oh, god...I can't watch it. It is truly awful. The techno-crap, the cruddy acting, the awful writing...
Enterprise: I like it for the same reasons I liked TOS when I first saw it -- the spiritof adventure, the characters. They've cut way back on the technobabble and that's made it much more tolerable to me. Bakula's the weak point for me; Trinneer makes the show.
Overall, I always prefered B5 to the TNG/DS9/Voyager stuff, and Farscape blows the doors off Trek for me.
"War is an ugly thing but not the ugliest of things; the decayed and degraded state of moral and patriotic feelings which thinks that nothing is worth war is much worse. A man who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself."
John Stuart Mill