I don't really have any favorite scenes, so to speak, so if it's okay, I'll just share my experience watching the movies.
I didn't watch the first or second film until after I was in college, in 2005. At that point, I rented all three and marathonned them in two days, just to see what the fuss was about.
I was blown away. The first one was one of the most intense films I had ever seen, and I knew as soon as I finished it that it was one of my favorite movies. I liked the second one as well. At that time, not knowing the third film had a negative reputation, I thought it was significantly worse than its two predecessors--but still not an awful movie, just a weak Terminator film.
I did notice a trajectory for the series: it kept getting softer. And here's where my opinion diverges from what I believe is most people's. Experiencing the movies back-to-back, the first film really, really
hit it out of the ballpark for me, shook me to the core, and the other films didn't. When I looked up people's opinions, I was shocked to find that people preferred the second, as the first was clearly better from where I was sitting in 2005.
Last Sunday the Terminator franchise turned 30. On October 26 1984 James Cameron made one really amazing film which was succeeded by an even more amazing sequel
...So I'm going to have to disagree with this. However, time has given me some perspective here, and down the years, I've come to appreciate what both films bring to the table.
I'll say that from the outset, The Terminator
established everything I'd come to love about the franchise. It was cold, almost dystopian in its presentation, even of the modern day. Aesthetically, 1984 felt a lot like the future. It had a smoky, noir-ish vibe to it. I loved the fact that two fragile humans (even Kyle Reese, while a soldier, seemed debilitated, weary, weak compared to the oppressive Terminator) were up against a seemingly unstoppable force, this thing
with no remorse, no empathy, no fear. I loved Sarah Connor's victory at the end, and the sense of dread that followed it. It was a perfect film; it hit every quarter note, half note, and beat, the narrative operated in perfect harmony with the action, and nothing ever felt like it dragged on. I remember watching a special feature where one of the crew (possibly Cameron) said that they made sure exposition was dispensed during the car chase. That way, neither the action nor the exposition existed in isolation. It was this minimalist approach that made me appreciate how the film was constructed. Simply put, action films tend to be boring pretty often. There's lots of noise and energy, but not a lot of intensity. The Terminator was constructed in such a way that the threat consistently builds to a climax, and the threat is both explained and shown to the audience.
This show-and-tell approach is so rarely done well, if it's attempted at all. Let's take a second to appreciate that it was pulled off so perfectly in what was essentially a low-to-mid budget B-movie.
Terminator 2 was a worthy follow-up. It felt open, bright compared to the first. It went a step further than the first in exploring questions about humanity and war, and doing so artfully. It basically took the narrow, shadowy corridors of the first film and exposed them to the light, forging an epic that solidified the identity of the series, sort of like what The Empire Strikes Back did with Star Wars. That said, I really missed the raw intensity of the first film, and having a terminator on our side made things far less intense for me. I also think it's visually significantly less interesting, which doesn't sound like a big deal, but it doesn't pull me in the way the first one did.
That said, where the first one had a theme of determinism and death, the second one had a theme of free will and hope. All of the changes were appropriate. I wouldn't change a thing about Terminator 2. I particularly love how subversive it is to the series' mythology, playing on all of Sarah's (and our) expectations. The first movie gave us a closed loop and a heartless machine; the second one, defying all expectations, gave us a split timeline and a machine-turned-E.T. How many big-budget sequels so effectively--and successfully--undermine established mythology? Again, we have a case of brilliant writing wrapped into a simple plot.
Thus, whichever you prefer, I think it's rare to see two films that complement each other so well (Alien/Aliens is the only comparable example I can think of--and, as might be expected, I prefer Alien). I'll always watch both back-to-back, the way I first experienced them.
I haven't seen Terminator 3 since 2005, but I think I could enjoy it as fanfiction. I've never seen any of the subsequent Terminator properties, so I can't comment on them.