bozon,
I share your disgust with films that pretend to be based on the historical record and have nothing to do with it. I haven't seen 300, but I probably won't given what I've heard about the embellishment.
Dowding,
You have a good point that the absolute accuracy of ancient historians is often in question. Still, from what I've heard of 300 it takes liberty to run miles away from anything the ancients ever recorded. I have no problem with fantasy, but when it confuses itself with history (Last Samurai) I have a big objection. Historical inaccuracy is a valid criticism in films that act like they are historical works.
laser and grunherz,
I don't care if this version is based off a comic book, it has presented itself as historical in its publicity and that is just not cool for me. Too few people now a days have a real appreciation for history. It's hard to encourage good historical perception when you have terentino, cruise and many others caching in on psudo-history.
I caution you in thinking Letters from Iwo Jima was completely a historical film. It was Clint Eastwood's presentation of history, and while I agree with his presentation, it is only that. It is not actually what it was like on Iwo Jima. Nothing can be. The difference between Eastwood's film and some of the other farce-history films is that Eastwood acknowledged fully that he was making a presentation, and kept as closely as possible in a cinematic format to the historical record. If you watch the credits you will see actual images from the battle that Eastwood has directly portrayed in the film. Still, it is only a portrayal. Wonderful, but it can never be complete.
Goth said it best with, "I never go to hollywood to get a history lesson."