We've talked a lot about what we don't like, so I'm curious to hear what your ideal let's play/let's player would be. My ideal let's player/story teller would be someone who has interesting ideas and fun/unique gameplay. I like stories, generational style play with some twists and turns, but not overly full of drama or clichés. I'd also like them to value the time of their audience and not create empty episodes or stretch videos out so they can get more ads. Just a decent human being with a penchant for storytelling, please! I have yet to find anyone that checks all these boxes, but I keep looking.
I like generational play - watching families grow up, not with too much blatantly obvious manipulation/cheats/editing being used. I like things to progress fairly steadily, with all aspects of the game being used, and while drama and a bit of chaos keeps things entertaining, let it have a long-term impact on the storyline. Don't just do things, and then next episode have it forgotten, let there be natural progression.
In respect of the Youtuber themselves: someone who can talk clearly, does not shriek or wail or babble memes all the time, and doesn't edit their videos into a hyperactive mess. Someone with a bit of charisma and charm and good cheer, but who does not inject too much of their personal life into the gameplay.
And this is purely personal and subjective - none of those mods which inject lots more graphic sex and violence into the gameplay. I don't play Sims for that, and it makes it so seedy and unpleasant. Whiny Brit did a couple with the Extreme Violence mod and I just turned off immediately.
James is my favourite currently, though he is VERY guilty of stretching both individual videos and the Lets' Play series out for too long. I don't think he has one, but a good editor would chop every episode down to 30 mins of brisker gameplay and he'd be much the better for it. But he does have a pleasant speaking voice, knows his stuff, and always -very amusingly sometimes- plays through the repercussions of his choices (such as the utter chaos that resulted from his student loan choices in the old University Lets' Play, or his vampire having the fatal flaw of being instantly unlikeable, which made raising a family with happy children *very* difficult)