Good ones, though I'm not as harsh on good ole' Abe. That episode is part of my childhood...
I'm going to go with Adonais from Who Morns for Adonais. I thought Michael Forest played the mythical character. I include him because, although he is a "god", people in the past did worship him as if he were real and not a story. If Jesus were to appear in a Star Trek episode, and his existence isn't actualy provable either, then it would be the same thing IMO...
If we are going non 'mythical' historic people from the past, then I'll go with Time Arrow's Jerry (Samuel Clemens) Hardin. Even though Time's Arrow loses its way, I thought his performance was the best part of the episode(s).
My least favorite historical character featured in Star Trek? Hmmmmm...Joe Piscopo. He is never mentioned by name, from that awful episode; but still the same, it was a terrible idea that, thankfully, I've only seen twice, and the second was over twenty years ago!!!
Rob