Sabertooth (X1) vs Sabertooth (Origins)

Except those were Logan's memories of his unaltered time line. We also see him stabbing Jean, who we see alive at the end of the film in the changed time line. We also see Cyclops alive, who dies in X3. Also, as we will see very soon, Deadpool is different now as well. Another thing to remember is that Logan specifically told Xavier that he had an issue with remembering anything after 1973, to which Xavier told him something like welcome back, realising what this meant with regards to the changed time line.

But you are right to some degree. As I mentioned before, DoFP only alters the time line from 1973 onward, so anything from before that remains unchanged, such as the events of First Class or any part of Logan's life up until the events of DoFP.

That being said, the X-men films take serious liberties with continuity and the time line.

-It seemed that Origins took place mostly in the early to mid 80's with Stryker first meeting Logan sometime during the Vietnam war which America (Stryker) become deeply involved with from around 1961 to 1975.

-The Paris talks were in 1972.

I'd chalk that up as another huge continuity error, which these films have in spades.

edit: But VD's claim of "anything after 73 was changed" seems to be it. Which would include the majority of the Origins film.

X1 Creed seemed pretty tough, Logan never really ended up beating him, where as he stomped Origins Creed.