It's follows the Terminator Movies

Rating: 10/10 (24 May 2019)

Terminator Salvation follows after the events of Terminator (1984) and Terminator Judgement Day (1991)
The Original Endings is Dark, because in Behind the Scenes, where Marcus kills everyone, and that was Skynet plan, but lucky, it didn't happen, Marcus gave John his heart.
Terminator (1984) was the first Terminator movie, but Terminator played by Arnold Schwarzenegger was the villain.
Terminator Judgement Day (1991) was the second Terminator Movie, but the Terminator played by Arnold Schwarzenegger was the good, and the liquid metal played by Robert Patrick was the villain.
Terminator Rise of the Machines (2003) was the third Terminator Movie, Terminator played Arnold Schwarzenegger returns as the hero, and the Judgement Day begins and Skynet makes their move.
Terminator Salvation (2009) was the fourth Terminator Movie, without Arnold Schwarzenegger as the Star, and with the CGI Arnold Schwarzenegger showing before he was send to past of the year of 1984, and takes place in year of 2018.