When it comes to being historical films, on the other hand - there's plenty of scope for telling both sides. "Tora Tora Tora" comes to mind right away, as does the two Clint Eastwood films that looked at Iwo Jima from both the Japanese and American point of view (Flags of Our Fathers/Letters from Iwo Jima). The existence of those two films alone rather contradicts the idea that all modern war films are "all one-sided". You could also include the recent House of Saddam mini-series which was all from Saddam Hussein's perspective. And I'm willing to bet someone will do an OBL biographical film - possibly even a sympathetic one, and wait for the sparks to fly on that - before long.
Well, I suppose there are those, and you'd be right, although I wasn't thinking in that direction. They're still movies from a single viewpoint, each movie showing the other side. I'm thinking more in terms of a single sweeping epic featuring both sides with their own languages intact. Joyeux Noel which Kegg posted certainly is a good one along those lines, and I guess I'd have to include Gettysburg as well.
I fully admit I was wrong about there not being any modern movies showing both sides and they're more likely just few and far between, but I don't prescribe to the idea of movies having to be one-sided in order to root for heroes. The point of these movies is that they're unbiased accounts, showing faults from both sides and I don't think anybody is going to come out any more sympathetic for the enemy. And learning from an enemies' mistakes is the only way we can learn from history. More movies should be showing the big picture.
Though, I guess these days, Hollywood wouldn't go for movies with large amounts of sub-titles. These days, kids have low attention spans. I do feel however, that they give more of a sense of immersion rather than seeing someone speak english on the other side. And they're certainly better than the dubbing of voices, as I've seen lots of terrible dubbing done to Hollywood movies in French.