Although history is sometimes boring, it's important to get the accuracy correct when telling the story. After all, more people are going to watch a movie rather than reading a long, dusty tome about the intricacies of history. As a filmmaker, you owe it to the audience to have them at least as knowledgeable about your subject matter as before they saw your film.
Movies allow for a lot of interpretation. They allow for artistic shots, symbolism in costumes, tone, casting choices and music to create the image the director wants. In my mind, that means that the history should not be touched. Highlight certain things, hide others and make up what is missing - but stay true to what is true.
Unless a movie is being billed as historical fiction, it should be as accurate to the original as possible. People often have misunderstandings about historical events beacuse historical events like Braveheart are fictionalized to make them more exciting and more marketable. Other films that are not based on real events do not need to be as accurate.
Film is one of the most delicate mediums and one of the hardest ways to translate something for the masses. When it comes to historical events it is very hard to make something entertaining and historically accurate at the same time. The important thing is to do the subject matter as much justice as you can out of respect for the people involved. You cannot cut corners just to make people happy. You need to tell the story right.