I think what also tends to be ignored is that despite having Edward Furlong in T2, I'd make the argument that Terminator 2 is as dark if not darker than Terminator 1 and still retains a lot of the Sci-Fi elements of the first movie. The big difference really is the use of brighter color scheme in T2 and even that is mainly just the first half of the movie. The kills alone along with the visual thematic story-line are super dark for such a big budget action movie.
I'll be that guy and say I prefer Alien to Aliens. I just love the claustrophobic and tense atmosphere. The set design is incredible. It's still legit scary imo. Aliens is also a great film but I just prefer Alien. Honestly I think Alien is probably the best directed of all four of these films. And maybe the best looking film of all four of these.
It's close enough to where it boils down to whatever mood you're in when watching them, I think. I prefer the cast and characters of the marines over the Sulaco crew, but the direction and atmosphere of the first in unmatchable.
I know originally Cameron wanted to do T2 soon after the original, but due to disputes involving rights with various studios surrounding the Terminator IP he couldn't. But the below deleted scene from the first Terminator makes me wonder just how much of the T2 script he had worked out all the way back in 84.