Terminator Salvation is the first movie in what is going to be a three part series. The story is set in 2018 when the machines have taken over the Earth and humans believe that "John Connor will be the one to destroy the machines" is a prophecy. The movie picks up well from where the last movie ended and introduces us to the world of terminators, not like the ones we got to see in the earlier Terminator movies, where there was always a raging battle between the humans and the machines. The story still hasn't reached that far. The writers seem to be slowly developing the story line to get to that point in year 2029. In this movie we get to see the earlier versions of the cyborg T-800, which were in the first two editions, who are not as smart. But we also get to see a glimpse of T-800 in the final moments of the movie.
The movie has great visuals and all the actors have acted their parts well. But Sam Worthington in the role of Marcus has just stolen the show from the others. He gives a very believable performance and he has essayed all the emotions very aptly. Christian Bale in his role as John Connor is good and he gives a feel to the character.
The movie may not be as good as the first two installments of the franchise but it is way better than the third one.
So do not listen to anyone who says that the movie is not good, but go out to movie theatres and watch it for yourself as this is a movie made for the Big Screen.