So after watching Terminator Genesis I've decided to compile a timeline trying to make sense of how the series' timeline got so messed up. Oh, I'm not going to make sense of the timeline itself, that is asking the impossible. I'm here to document how it got to where it is in the first place. So here we go.
-Terminator.
This 1984 (relatively) low budget R rated action movie that started it all has a human resistance fighting and winning the war against the Machines led by Skynet. In 1997 Skynet started nuclear Armageddon to try and eliminate humanity. In its final hours in 2029, knowing all is lost, it tries a last minute gambit to send a Terminator 800 (T800) back to 1984 to kill Sarah Connor, mother of resistance leader John Connor, before he was born. The resistance send back Kyle Reves to stop it, and in the end the Terminator is killed, as is Kyle, but Sarah lives, Kyle turns out to be John's father and the remains of the T800 are found by a company which would later go on to develop Skynet. A stable timeloop is established with no instabilities in the timeline and no real plot holes.
-Terminator 2.
This 1991 high budget R rated action movie (which somehow has a budget which is just around how much the first one grossed when adjusted for inflation. How the hell did that happen? Lucky for them it was the most successful Terminator movie to date) is set in 1995, only 2 years before Judgement Day. The plot revolves around a T1000 being sent back in time by Skynet to kill the young teen John Connor, while a reprogrammed T800 is sent back by the resistance to protect him. Long story short the T1000 is destroyed , most of the research regarding Skynet is (believed to be) destroyed and the T800 sacrifices itself to make sure nothing can be used from it to develop Skynet. The movie ends on an optimistic but very open note, leaving to the possibility that things will not end in nuclear Armageddon, though a stable timeloop is still quite possible (there is a non-cannon alternate ending where the world is shown to not have ended, but it is an alternate ending for a reason). Though one can question why the T1000 wasn't sent back in the first place, or why a reprogrammed T800 wasn't sent in Kyle's place, the plot holes are minor and the timeline still makes sense.
-Terminator 3.
This is where things start to loose cohesion for the timeline from this 2003 movie. Right off the bat it's 2004 and judgement day has not occurred. A T1000 (named the T-X but it's just a T1000 when you get right down to it) is sent back in time to kill the leaders of the resistance, not only John Connor but also his generals who have no protection what so ever. It achieves this before the T800 sent back to protect John (again) manages to kill it. John Connor and his wife end up in a nuclear bunker when the nukes start to fly. The plot holes start to take real weight in this one, as the T1000 kills quite a few future resistance generals and other leaders in the war, which it should then not know to kill in the first place as it never would have had reason to kill them in the past if they never become important in the resistance. Another plot hole is that despite the nuclear bombs flying 7 years later things in the future still end up more or less the same, the only logical explanation for the two previous instances of time travel happening in the first place being possible due to a stable timeloop which the universe is dependent on being active and stable. Another plothole is that the reprogrammed T800 supposedly killed John Connor in 2033, 4 years after Skynet was destroyed, though weather or not this is actually a plot hole is debatable as the T800s could be operating independently from the rest of the machine network.
-Terminator Salvation.
This 2009 PG-13 Terminator movie. Despite it all, the movie doesn't contradict that much of what has previously been established as part of the time loop other then having judgement day be in 2004 instead of 1997. The movie takes place in 2018 and had it not been for the date of the date used for judgement day no plot hole would have arisen, though since it does that means it is firmly in the part of the timeline which is a jumbled mess instead of a clean timeloop. (on a site, though it ended up being profitable, due to under-preforming and the company which owned the movie rights to Terminator at the time going under, the planned trilogy it was beginning was axed. Probably for the better)
-Terminator Genesis.
This one takes the cake. Another PG-13 Terminator movie (whoever thought that was a good idea should look at Salvation's sales numbers compared to Terminator 2). The movie starts in by giving us the backstory of the setting, which has judgement day taking place in 1997 once again. Quickly moving to 2029, the movie shows us part of the final battle against Skynet as well as the first T800 being sent back in time to 1984, as well as Kyle being sent back as well. John Connor is shown to be captured in some way by a different type of Terminator, though this doesn't create any plot holes. What does is that minutes after arriving back in 1984, the T800 is destroyed by a combination of a reprogrammed T800 and Sarah Connor, while Kyle is attacked by a T1000 before being saved by Sarah and the reprogrammed T800. Over the course of the movie the following plot holes arise: despite being sent back in time first (and thus writing, or rewriting, history) the T800 and Kyle arrive after the T1000 and years after the reprogrammed T800 which saved a 9 year old Sarah from another terminator sent back to kill her. This physically should not be possible, as the timelines which sent all three terminators (evil T1000 to the more distant past, good T800 to the more distant past and evil T1000 to 1984) will not have exsisted to send them back in the first place, and as such would not disturb them, as doing so would mean John is never born and thus never gives a reason for the original T800 to start the timeloop in the first place. There is also the fact that John is never born at all in this new timeline, judgement day is moved back to 2017 before being averted altogether, and that as a result of the new timeline breaking off from the stable timeloop (which should logically be impossible) no one who was sent back in time except Kyle will ever even exist, and Kyle will not be either (and the him who lives to reach the age of being sent back is a completely different person).
Genesis not only accepts the time travel induced plot holes of the series, it takes them and sees if it can make a whole movie around them. Though it entertains I can't say it's memorable or good by any stretch of the imagination.
Anyway that's a breakdown of the timeline of the Terminator movies going downhill in terms of logic. I'd have added in the Sarah Connor Chronicles, but that's just another layer of headache to try and deal with, coupled with the fact that the cliff hanger ending it got before being cancelled actually manages to make things worst the Genesis and it is never resolved.
-Terminator.
This 1984 (relatively) low budget R rated action movie that started it all has a human resistance fighting and winning the war against the Machines led by Skynet. In 1997 Skynet started nuclear Armageddon to try and eliminate humanity. In its final hours in 2029, knowing all is lost, it tries a last minute gambit to send a Terminator 800 (T800) back to 1984 to kill Sarah Connor, mother of resistance leader John Connor, before he was born. The resistance send back Kyle Reves to stop it, and in the end the Terminator is killed, as is Kyle, but Sarah lives, Kyle turns out to be John's father and the remains of the T800 are found by a company which would later go on to develop Skynet. A stable timeloop is established with no instabilities in the timeline and no real plot holes.
-Terminator 2.
This 1991 high budget R rated action movie (which somehow has a budget which is just around how much the first one grossed when adjusted for inflation. How the hell did that happen? Lucky for them it was the most successful Terminator movie to date) is set in 1995, only 2 years before Judgement Day. The plot revolves around a T1000 being sent back in time by Skynet to kill the young teen John Connor, while a reprogrammed T800 is sent back by the resistance to protect him. Long story short the T1000 is destroyed , most of the research regarding Skynet is (believed to be) destroyed and the T800 sacrifices itself to make sure nothing can be used from it to develop Skynet. The movie ends on an optimistic but very open note, leaving to the possibility that things will not end in nuclear Armageddon, though a stable timeloop is still quite possible (there is a non-cannon alternate ending where the world is shown to not have ended, but it is an alternate ending for a reason). Though one can question why the T1000 wasn't sent back in the first place, or why a reprogrammed T800 wasn't sent in Kyle's place, the plot holes are minor and the timeline still makes sense.
-Terminator 3.
This is where things start to loose cohesion for the timeline from this 2003 movie. Right off the bat it's 2004 and judgement day has not occurred. A T1000 (named the T-X but it's just a T1000 when you get right down to it) is sent back in time to kill the leaders of the resistance, not only John Connor but also his generals who have no protection what so ever. It achieves this before the T800 sent back to protect John (again) manages to kill it. John Connor and his wife end up in a nuclear bunker when the nukes start to fly. The plot holes start to take real weight in this one, as the T1000 kills quite a few future resistance generals and other leaders in the war, which it should then not know to kill in the first place as it never would have had reason to kill them in the past if they never become important in the resistance. Another plot hole is that despite the nuclear bombs flying 7 years later things in the future still end up more or less the same, the only logical explanation for the two previous instances of time travel happening in the first place being possible due to a stable timeloop which the universe is dependent on being active and stable. Another plothole is that the reprogrammed T800 supposedly killed John Connor in 2033, 4 years after Skynet was destroyed, though weather or not this is actually a plot hole is debatable as the T800s could be operating independently from the rest of the machine network.
-Terminator Salvation.
This 2009 PG-13 Terminator movie. Despite it all, the movie doesn't contradict that much of what has previously been established as part of the time loop other then having judgement day be in 2004 instead of 1997. The movie takes place in 2018 and had it not been for the date of the date used for judgement day no plot hole would have arisen, though since it does that means it is firmly in the part of the timeline which is a jumbled mess instead of a clean timeloop. (on a site, though it ended up being profitable, due to under-preforming and the company which owned the movie rights to Terminator at the time going under, the planned trilogy it was beginning was axed. Probably for the better)
-Terminator Genesis.
This one takes the cake. Another PG-13 Terminator movie (whoever thought that was a good idea should look at Salvation's sales numbers compared to Terminator 2). The movie starts in by giving us the backstory of the setting, which has judgement day taking place in 1997 once again. Quickly moving to 2029, the movie shows us part of the final battle against Skynet as well as the first T800 being sent back in time to 1984, as well as Kyle being sent back as well. John Connor is shown to be captured in some way by a different type of Terminator, though this doesn't create any plot holes. What does is that minutes after arriving back in 1984, the T800 is destroyed by a combination of a reprogrammed T800 and Sarah Connor, while Kyle is attacked by a T1000 before being saved by Sarah and the reprogrammed T800. Over the course of the movie the following plot holes arise: despite being sent back in time first (and thus writing, or rewriting, history) the T800 and Kyle arrive after the T1000 and years after the reprogrammed T800 which saved a 9 year old Sarah from another terminator sent back to kill her. This physically should not be possible, as the timelines which sent all three terminators (evil T1000 to the more distant past, good T800 to the more distant past and evil T1000 to 1984) will not have exsisted to send them back in the first place, and as such would not disturb them, as doing so would mean John is never born and thus never gives a reason for the original T800 to start the timeloop in the first place. There is also the fact that John is never born at all in this new timeline, judgement day is moved back to 2017 before being averted altogether, and that as a result of the new timeline breaking off from the stable timeloop (which should logically be impossible) no one who was sent back in time except Kyle will ever even exist, and Kyle will not be either (and the him who lives to reach the age of being sent back is a completely different person).
Genesis not only accepts the time travel induced plot holes of the series, it takes them and sees if it can make a whole movie around them. Though it entertains I can't say it's memorable or good by any stretch of the imagination.
Anyway that's a breakdown of the timeline of the Terminator movies going downhill in terms of logic. I'd have added in the Sarah Connor Chronicles, but that's just another layer of headache to try and deal with, coupled with the fact that the cliff hanger ending it got before being cancelled actually manages to make things worst the Genesis and it is never resolved.