If it were up to me, I would have ended the Terminator franchise with Salvation being the third and final film. Of course, the Universal Studios ride is what Salvation should have been.
I enjoyed the new movie and felt it was better than the tripe that followed Terminator 2, but it also felt like they took the easy route with a story line similar to the first two movies.
There are plenty of original films if you look for them, but, yeah, they so often do take the "easy" way out and make sequel after sequel of existing franchises, or worse (usually) reboot them. I'd certainly like to see a higher ratio of original films versus extending existing stories..