I never considered Black Orchid to be a historical simply because it's set in the 1920s but have listed it anyway. Same with An Unearthly Child. The Aztecs, The Reign of Terror and The Crusade were all powerful stories, and I don't doubt Marco Polo would be if it were in existence. When the production teams began using historicals as comedy entries they began going downhill, and I guess that could be attributed partly to the demise of the historical 'genre'.
I liked "The Aztecs" better than "The Romans". I can't comment on, or consider voting for, the others because I haven't seen them. Aside from the two already largely discounted in the opening post.
The Aztecs is not only my favorite historical, it's also my favorite First Doctor serial. That being said The Reign of Terror, The Crusade, and Marco Polo are all incredible stories.
Wish we could vote for a top three, and also that the poll could be split between surviving and lost stories, IYSWIM. I went for The Aztecs, as I don't think I can really vote for one I've only heard, but The Massacre, Smugglers and Myth Makers might all have been in the running if it weren't for that.
I love the historicals and could easily vote for about 6 or 7 of these but I've gone for Marco Polo as even just on audio it's one of my favourite Who stories. Personally I don't count An Unearthly Child or Black Orchid - the former wasn't really intended as a historical and the latter is absolute crap and seems more like the writer had a spare script he wasn't able to sell to a detective series.
Given that I've seen precious little Hartnell I don't feel I can judge. I'd really liked to have seen the Highlanders though.
The Aztecs by a mile for me, but admittedly, I haven't heard a lot of the soundtracks/seen the recons.
I have to go with the Romans. It's light and cherry, we get to see the Doctor burning down Rome, (after a fashion), impostors, Nero, and Barbara & Ian finally getting it on. Two thumbs up.
An Unearthly Child doesn't belong on that list. It was about cave men. Not exactly something based upon historical records. Unless you're thinking about episode 1 being an historical set in 1963, in which case, OK! I'll be honest, though, bearing in mind that many stories on this list are currently lost or incomplete (unless you've been able to track down a fan-made reconstruction or bought the audio versions or read the novelisations), of the one I've seen I've never been that fond of the historicals. Black Orchid was deadly dull for even a 2-parter. The Aztecs was more of interest in retrospect because it established the "fixed point in time" concept that the revival has featured heavily. The Romans was amusing. The Gunfighters is one of my least-favorite stories of all time. An Unearthly Child is a much better story than people give it credit for, but, really, it becomes irrelevant after episode 1. I suppose The Crusade could be up there if it were complete in the archives. Likewise, I've heard enough good things about Marco Polo that assuming the memory isn't cheating a lot of people, it'll be a good one to watch if it's ever found. But I really don't like any of the remainders enough to cast a vote. I'm much more partial to the SF historicals, stuff like The Talons of Weng Chiang, and some of the more recent hybrids like Girl in the Fireplace and Vincent and the Doctor. If they were on the ballot, I'd probably do a coin toss between Fireplace and Vincent, maybe with Vincent having a slight edge because Tony Curran was so cool in the role. Alex
Of those serials incomplete or missing entirely, I base my opinions on them entirely from the fan reconstructions, most of which are pretty damn good. Marco Polo's reconstruction is particularly well made, which may or may not effect my overall opinion of the story, but I still think it's pretty damn good.