I found a quote from Rod Sterling, the maker of The Twilight Zone, saying that:  "it is said that science fiction and fantasy are two different things. Science fiction is the improbable made possible, and fantasy is the impossible made probable."

I thought that this would be a good quote to use in the opening of my project, because it links directly to my main point about realism. I think that I could expand upon the concept further, and go into detail about how the genre as a whole needs to have a basis in reality, unlike the fantasy genre. 

Here are some key scenes from each of my films:
The Thing - The dog (first use of effects), Norris transformation, the climax (big Thing), stop-motion deleted scene.
Alien - Nostromo landing, chest buster, climax (air lock).
Terminator 2 - T1000 scenes (use of CGI), removing the head chip (prosthetics)
Avatar - need to rewatch, but most action scenes would be useful.

I'll also rewatch these films with the commentary to see if there's any interesting about the choice of effects or motivations.

There's a book in the library all about the special effects in alien, which will be very useful.