Just like I said only believe the basics in the games and the doco's, but for the best information ever Books, books, books they are the best and most reliable sources, but not just one but many on the same subject. eg. if you want to learn more about tanks in particular don't just read one book read 10 different ones and compare the facts and figures. You will probably find that some of the figures dont match up but are relatively close. Same as if you see a fact in a book, to verify whether it is most probably true read others then compare and if three other say the same thing it is probably ture.
But anyway I have found ww2 very interesting since as long as I can remember I consider myself to know a little about alot of things I don't specialise in one particular area, I do find certain areas more interesting then others of course. I have read many books and seen many documentaries as well, movies 'play' the facts to make a good story, here is a website to tell you what I mean about lack of historical realism in movies.
Saving Private Ryan mistakes, goofs and bloopers
and about games remember it is a game not fiction, it is made and changed to be fun, if the designers don't like the fact that the germans didn't have many tanks on the contentin peninsula (D-day utah beach) they will change it and give you the ability to have for example the 21st panzer divison that is fiction, the Germans only had old french tanks in that area and still there werent enough to make a real good use out of them.
But good learning anyway, we all start somewhere.