Cue the 'I'll be back' jokes as we have ourselves another Terminator movie. The good news is that this better than the last two sequels. The bad news is that, at best, it is just decent and is in no way on par with the first two films.
You may have heard that Genisys involves a lot of time travel and that it makes the plot rather confusing, but nothing could be further from the truth. Here's the basic plot. We start in the future, where the war with the machines is raging on, and Skynet has sent a terminator back to 1984 to kill Sarah Connor. Naturally, Kyle Reese is sent back as well to protect her. But as he travels to the past he starts to have memories of the past, but not memories of a past he had lived. When he gets to 1984 he realizes it is not the past he is expecting, and certainly not the past that led to the future he just departed. This is because someone or something from the future went even farther back into the past a changed events that altered their future which affected the past to which the current future has traveled. In fact, the past that we were expecting no longer exists and is, in fact, in the past (a past past, if you will). When Reese gets to the new past he finds that Sarah wants to travel to the future. But it's not the future that Reese came from, but a point in between which would still be the future for Sarah but the past for Reese, but not the past he remembers as it doesn't lead to his current future which is now in the past. This, of course, is to prevent the future that Reese came from from ever happening, but thanks to events in the past that were changed by the future, that future doesn't exist anymore and is, in fact, in the past (a past future, if you will). Instead, based on Reese's memories of past that isn't his past nor the future Sarah expects, and not the past that lead to the current future which is now in the past, they travel to another point in the future, but again somewhere in between the future from which Reese comes and the future to which Sarah wanted to originally travel but is definitely a future that will be the past of the future that is coming but hasn't happened yet (a future future, if you will), but will be the future based on the events of the past that were changed by the future, but the past future not the future future, which while still to happen in Reese's future is part of his past, but his future past, not his past past. Again, this is all to prevent the future from happening but this time not the past future based on the past past, but the future future which is based on the current past which was changed by the future in the past, but not the future that is now in the past but rather the future that may happen if when they get to the future of the current past they can't change things and make the future future part of the past and thereby create a new future, which would be part of Reese's past but would still occur in his future. So, as you can see, it all makes sense. It is explained best in the movie when the terminator says something like “time travel is easy because of reasons so you should just accept it”.
As a whole the movie is a bit of a mess (see preceding paragraph). The acting is generally pretty bad, except for Schwarzenegger who actually gives the best acting performance of the movie. I even like the explanation they give for why, even though he is a machine he looks older. J.K. Simmons is good too but his role is rather small and somewhat goofy. Everyone else though is awful, even Jason Clarke who is usually quite a good actor. The action sequences are pretty good, but the special effects are a bit of a mixed bag. One of the weirdest special effect occurs when Schwarzenegger's terminator has to fight a younger version of himself. The younger Schwarzenegger is created by digitally enhancing his face to appear younger and ends up looking exactly like Schwarzenegger's face being digitally enhanced to look younger. Its kind of creepy.
I did like the basic idea behind the movie and having the time travel essentially allow the last two sequels to be disregarded (sort of like was done with X-Men: Days of Future Past). However, they end up changing a bit too much and it's no longer clear if anything of the first two movies exist in the timeline they have now created. And while I did not think this was a good movie overall, I was entertained enough at times to be interested in seeing what may happen with a sequel (although truthfully I expect it to be bad if it happens). I just hope that they figure things out a little more clearly by then. Of course, if there is to be a sequel, I will have to wait for the future. Or is that the past? I'm not sure anymore.