I think the genre of historical drama should be renamed historical fiction all around. History is never accurately represented in these movies, even shows on the history channel tend to make generalizations for the purpose of time and for accessibility. These type of movies tend to make a hyperbole of either how villainous or how heroic a particular figure was. That being said, my opinion of historical dramas is based totally on taste and not what so ever based on actually fact (since its my presumption is that that these things have little to no historical value).
Depending on how drunk I am, I think that Braveheart and The Patriot deserve a rank of anywhere from "decent" to "fucking great". I don't know if There Will Be Blood ranks as a historical drama, but it is my favorite movie that I've ever seen. I can't really think of any other historical dramas I've seen. Gladiator maybe, since it is probably about as historically accurate as Braveheart. With the exception of There Will Be Blood, all of those movies are just "neato, fun, entertaining" movies). Thinking about it, maybe Gangs of New York counts as historical drama (depending on how far we are willing to extending our sense of historical disbelief), and that movie is just awesome, and is also notable for being the only good movie Drew Barrymore has ever played in. I am looking through a list of historical dramas on wikipedia and A Knights Tale came up, which I really like, and is based on a Geoffrey Chaucer story, which is based it on one or two different knights lives, according to the wikipedia article, which is based in irrefutable fact. (witchfinder general was a film that came up, and i have never seen it, but witchfinder general is a a pretty decent premetal-psych-rock band, and if you look up the history of witchfinder general its kind of sadly funny). Titanic was also on there, which was just kind of whatever to me, but I didn't think it was terrible. Also Charlie Wilson's War, which I thought was great, but I don't know all of the TRUE history behind it so it might be a total let down. Other movies on the list that I like include: Frost/Nixon, Milk and Wonderland. Again I really enjoyed those movies, but we have to question their historical merit.