Ever since I saw it at the age almost 8 years old, I fell in love with TOS. Up to that time, spaceships were rockets, and flying saucers. The Enterprise was so unique. The series showing different races, and aliens living in peace, was an important lesson, too. I credit ST with helping me start to look at all people as the same. Even now ST TOS gives me that sense of wonder feeling, that no other ST has done.
TOS, mainly because it was the first "Star Trek" I ever saw, and it was the benchmark that all that came after it was measured against. I really liked TNG, and also DS9, although I didn't really watch it regularly during the initial run. I missed a few earlier episodes all of the last three seasons of Voyager, and still have not seen them. I finally have seen all of DS9, thanks to SpikeTV. I have to say that I enjoyed Enterprise, also, but it wasn't great. There were a few individual episodes that I really loved, but overall it just went in the wrong direction. I did really like a couple of the characters, and wish that they could have had more time for development...perhaps if Berman and Braga hadn't been involved at all, things might have been better, and it might have lasted longer. Who knows?
With me, it is what I grew up with. TOS was the main area for all other shows to come from. Even in Enterprise, they always refer to something in the TOS world. Weather it is Flox using a Tribble for dinner, or Even the Great USS Defiant in the Mirror Darkly episode.
Only good thing is how the later shows 95% of the time stayed to the Star Trek Bible and kept things in line. Where the TOS episodes sometimes jumped from one reality to another.
I think the TOS stories were much better overall than later incarnations. There were many classic sci-fi stories adapted to ST:TOS such as Arena, the short story on which it is based I read many years later after having seen the ST version. I kept noting the similarity to the episode and found out later that there was an actual connection.
While there were some really great episodes and ships and action in the later series, none consistently appealed to me in the same way. They were all a little too influenced by the soap operas and such, it seemed to me. I like my sci-fi action/adventure a little more straightforward.
I heard that a few ideas and scripts made for the TOS shows, that never got into production because of the series being cancelled, were used in TNG shows with names and such changed to adjust to the newer style show. Just can't remember which ones.
The season one episode about the alien being impregnating Troi may have been one such episode or maybe it was recycled from the ideas/scripts for Phase II. I'm sure it was recycled though.
There are, for me, some really great episodes from all the series except perhaps Voyager (to be fair I quit watching Voyager sometime during the second or third season). But the original is the one that I can pop into the DVD player and feel right at home while at the same time driving everyone around me nutso.
Hmmm... you stopped watching it? could it be because Voyager stunk... A LOT! sheesh... I watched that show and was frustrated with it because every so often there would be a really good show, a little less than 25% of the time, another 25% were enjoyable, but nothing special and 50% of the time the show just reeked. The characters were lame: Janeway... in a word 'Boring', my mom as ships commander, yes she had some decent character stuff occasionally, but I like my Captain to pack an old fashioned punch. Tuvock the vulcan, not because he was black, still is for that matter... I've got no problem with that, even though I know trek purists who did... but because he was uninteresting for the most part, they really didn't cover any new ground with him. The Maquis were mildly interesting, but the Federation people were too bland. I stopped watching for a while too, but came back when they had the borg episode... I came back for the borg and stayed for Jeri Ryan...brilliant casting there... yes it was often as mindless as watching baywatch, but at least there was something to watch even during the stinky episodes.
Like many of you have stated, TOS was my first Star Trek love. The early episodes featured what was then considered, high caliber actors, and the scripts were written by some seriously talented writers who have since gone on to much greater heights. Without naming names, these were well written scripts, and genuinely good stuff. Mostly morality plays, as much of Star trek was and still is, they were meant to be reflections of current events. The Cold War, the arming of countries by our Industrial Complex, bigotry, and much more. I did enjoy some of the "Next Generation" episodes, but they were only a substitute to my early infatuation of this great classic show. Voyager was so-so at best, although I did like the Ship and the new hardware, the plot was less interesting. DS9 was more of a "soap opera" style show in my opinion. There are a few "Dominion War" episodes I did like for all the Star Ships in dogfights seen on them. Overall, and this is probably because I'm an old fart who prefers the 60's and 70's than anything I see nowadays, TOS still rules!
For me, it's TOS - but the Movie Era. For some reason, the ship designs from ST:TMP thru the first ten minutes of ST:GEN (on the E-B) appeal to me much more than the TOS designs. Especially the uniforms.