It was in the past. Today, more people are literate, so people not involved in wars are watching and writing about them. Plus, the losing faction is not wiped out, thus they are able to tell their side of the story.
No. If you study World War II in the US you will see one side of it. If you study it in Japan you see a whole different side.
It's a common saying that has had some truth in it but, no, it's NOT always written by the winners.
When I was at school in Australia (in the 1940s) I learned England's version of history. It certainly painted England in a favourable light compared to the empire they had conquered. (Oz was still a British colony until 1901 when we became a nation.) During the '40s we were still part of the empire and their influence permeated Australian culture.
Sometimes. Up until grade 9, like Didge, I also learned England's version of everything because Britain has been had a very big influence on our 'culture,' and we're part of the Commonwealth. It was only last year that we started to learn more about both sides of history. I think that now that we have access to both sides of the story, we can see both perspectives whereas before we didn't, and History is becoming less one-sided than it was before.