I really only liked the original.
The Terminator (1984) was a game-changer in scifi genre movies, stringing together themes that have inspired countless other movies. Every succeeding sequel has failed to match the brilliance of the original, even if the first sequel (Judgment Day) is still rated very highly. But since director James Cameron left the franchise, the quality of the work has been shoddy and Genisys might be the worst. Primarily because it is such an obviously cynical attempt to appeal to the franchise faithful.
In that light, perhaps it’s no surprise that Genisys fails artistically and creatively, to justify its existence whatsoever. At least one might argue that the third (Rise of the Machines) and the fourth (Salvation) instalments were genuine attempts to continue the narrative. Genisys, however, is a complete mess – functioning as some kind of misguided collage where time travel is utilised as a device to mangle the original storyline beyond recognition.
It is not cleverly done at all – it’s just a convenient excuse to get killing machines into battle and throw issues of continuity out of the window AND above all, exploit a very recognisable brand name! The producers have indicated their confidence in the new retcon with subsequent sequels to be released in 2017 and 2018 respectively.