I have watched this twice - in original release on Fox TV in 2009 or so, and ten years later in 2019. It consists of a short first season (short due to a screen writers' guild strike) and a full second season. The first time I missed a lot of neat plot points and twists, and missed how well constructed it was (little stuff linked together after many episodes). This show would have survived with Netflix and binge watching. On regular TV with a weekly delay plus missed weeks plus seasonal delays and hiatus and interruptions, it was hard to keep track of the major plot lines much less the intricacies. And with the series the devil is in the details (or "complications", a horologist joke made in one episode and popping up a couple episodes later).
This is not a "Terminator of the week" show. It's a true serial. Even with episodes that seem to have self-contained stories, there is ongoing world-building and story progression.
At the heart of the story the elephant in the room is whether we should totally identify with humanity as the unblemished heroes. The key plot line which emerges is whether all AI's are bad, and there are clear examples of Bad Humans. There is a mundane love story full of betrayals, and the never fully-resolved question of whether there might be another love story as well. There's a mother clearly suffering from PTSD and a son who's pushed into a Messiah role he doesn't want. There's incredible Terminator battles and good humor ("can I kill the bird later?"). There are unanswered questions that still bug me (was the apparent liquid metal Terminator made, or taken over? - listen carefully to the conversation between Weaver and the detective towards the end of season 2).
The last 3 or 4 episodes stand out. I get the impression the writers and producers knew the series would not be renewed and went out in grand fashion - giving us almost the main plot of what could have been a full third season in just the final four episodes. Amazing work, and fully committed performances from the actors.
I still don't know if Cameron evolved into a self aware, emoting - as well as thinking -being, or was just improving her infiltration skills through complex but not- AI level algorithms.
Also in the final episode you need to replay the emotions that cross John Connor's face when he sees someone he thinks he has lost forever, only to realize the person looks the same but isn't. Is that disappointment not joy? I think it is disappointment and makes you rethink everything the series has been about.
The first Terminator is one of the greatest action science fiction / evil computer movies ever made. The TV series is the best TV science fiction series I can think of, and that includes all the great cable TV shows.
A note in the actors: Headley was criticized at the time for basically not being Linda Hamilton. On second viewing I think she is outstanding. Connor is super, better than T2. I can't decide whether Reese is good guy or a bad guy. He's definitely a murderer, rare for a hero (I'm not counting enemy combatants).
Best line in the series: "I'm sorry I ever doubted you" - delivered by John seated across from his mom. See if you don't agree when you watch that episode, for reasons that will probably surprise you (surprised me!).