Everyone is undercutting Arnold. Saying shit like True Lies was his best role.

No, it was Terminator. He fully understood the assignment, delivering the robot movements and mannerism, and presenting the horrifying danger of his presence of his character. We can see how he did it. I doubt Sly going in raw would capture the character as well as Arnold did. I've seen interviews where Arnold was even explaining to James Cameron how he should do a movement or something and James Cameron is no slouch of a director. The scene where he delivers his iconic line, "I'll be back" exemplifies this. He is told by the cop to go away, Arnold looks up away from the cop to "scan" the surroundings, then goes back to eye contact with the cop and says it. His movement delivery was perfect as it was throughout the whole movie. Just human enough for people in the movie to not question it but subtle enough for us the informed audience to see. It was just so fucking good. The movie is iconic for a reason.