To be honest, I think the videogame structure of the film is kind of an afterthought. There's a number of periscopes in the film that indicate it was re-written rapidly and repeatedly and, well, obviously, sloppily as well. I think the basic idea is pretty good, and if the rumors about the original draft of the script are true, it could have been a brilliant movie, but the studio obviously got cold feet taking such a big chance with such a major franchise, and kind of bludgeoned the story in to a structure that didn't suit it at all.

That said, it's not a terrible movie, and it's far, far, far better than T3.  There are elements to it I super-muchly like. If anyone's interested, you can read my review online here http://www.republibot.com/content/movie-review-terminator-salvation-2009