When talking about any particular terminator movie it is impossible to discuss it outside of the context of the entire franchise. However, when Terminator was released in 1984, it was new and it was unique. At that time no one knew there would be more nor that the series would last for decades.
We first saw Terminator as a newly released movie in a theater in 1984. Although in the ensuing decades and sequels much talk would center around John Connor, leader of the human resistance, in the beginning the story was about Sarah Connor. In Terminator John does not even appear except in a brief flash forward. Our viewing of everything thing that has come after is based on this initial impression that the primary character is Sarah.
There exists an almost cult-like following of John Connor, even to the point of flaw. It has been remarked that several of the stories deal with modifying the terminators to make them more human, nurture rather than nature. This concept if first introduced in Judgment Day where young John attempts to teach the T-800 to act more human, culminating in the "I now know why you cry" moment. However, with John Connor the opposite is true. Mankind cannot win against the machines without him, and only him. Nature rather than nurture.
In Genisys Pops believes this in talking with Sarah about why she must "mate with Kyle Reese in this timeline".
We know that your son will be John Connor, and that the machines cannot be defeated without him. I do not see a choice.
As we wrote in the Chronologies we believe that in the original unaltered timeline it must be Sarah who rises to leadership of the resistance as there is no John Connor. She does this so successfully that Skynet determines it must travel into the past to kill her. This would indicate that it is not a single individual - John Connor - who must exist in order to defeat Skynet, but rather a human leader who understands that Skynet can be beaten and instills that belief in others.
This concept is also supported by conversations with the writers of The Chronicles. At the end of Season 2 John jumps into future. Because of this he never rose to leadership in the resistance and future Derek has never heard of him. After the series was cancelled the writers revealed that in Season 3 - which tragically never came to be - it was to have been Sarah who led the resistance as John was no longer around.
An even stronger example of this is in Genisys where not only is John Connor not the savior of mankind he is its enemy and it is Sarah who defeats him and defeats Skynet. As she says to Kyle …
John is not humanity's last hope any more.
Our biggest complaint is that within this cult-like mind-set about the great John Connor is the reduction of Sarah to the vessel. She is the Virgin Mary who is the vessel for the Messiah John. Obviously this is misogynistic, but it is also entirely unfair. In Terminator it is Sarah who guides and controls events once she understands they are real and true. She convinces Kyle, who would die for John Connor, to disobey John's orders and follow her in an attempt to destroy Cyberdyne and stop the war before it occurs. She is the one who confronts the T-800 face-to-face and destroys it. When she tells Kyle in a deleted scene "I am not a 'mission'" she is really saying 'I am more than just my uterus'.
In Terminator Kyle refers to her as
... the legend. Sarah Connor, who taught her son to fight, organize, prepare from when he was a kid.
Even though he is in love with her and in awe of her, Kyle's belief is that his mission is to protect and preserve Sarah's womb so that she can birth his leader and hero.
As Sarah says in Genisys
Look, I know you think you're here so you can just lock me in a room until I give birth to the leader of the Resistance.
Sarah's attitude, of course, is closer to 'Screw that!. I am a person, I can act, I can decide. I think we should hunt down Cyberdyne and blow it out of existence and stop the war from ever happening! ' And her idea is far superior to his as preventing the war means billions of people will not have to die regardless of whether there is ever a John Connor.
To attempt to push this dynamic woman into the role of simply being the Mother of the Savior does her an enormous disservice.
In Terminator, The Chronicles and Genisys the focus is on Sarah and not on John. He becomes "John Connor" because of Sarah. It is Sarah who crushes the T-800, it is Sarah who returns to Los Angeles to destroy Cyberdyne, it is Sarah who has hidden weapons at Enrique's, it is Sarah who leaves weapons in her crypt. The Chronicles is rife with Sarah leading, guiding and molding young John and in Genisys Sarah's attitude is almost "Yes, I birth the 'great John Connor', whatever. Don't bother me, I'm busy saving the world".
Our reviews of the stories is founded on this premise that the core character in them is Sarah and not John. This very strongly colors how we feel about each of them.