Do tell!
When looking at historical dramas, I generally assume that the events are going to be twisted and tweaked to make things more tv-worthy. What I look for, then, is if a production can capture the feel of a place and time by getting the small details right - how people dress, what the world they walk through looks like, and . I really like Master and Commander: The Far Side of the World for this. I understand that Rome is very good, too, though I don't know enough about Roman material culture.
In my period of expertise, Turn: Washington's Spies is mostly terrible at both big and small things, and The Patriot is entirely terrible at everything.