1. I think speed builds are better because the player focuses less on just the technical build aspects and more on the build theme.
2. Let's plays kind of bore me in general, to be honest, but I think what bores me the most is if the family never leaves the home lot.
3. Definitely attitude. If the video starts with the simmer in a grumpy or dreary mood, I'm likely to click away. As a YouTuber myself, I make sure I'm in a good mood before I record and never force myself to pretend to be cheery.
4. DEFINITELY personality of the player. There's TONS of gameplay out there. The thing that will make your videos special is YOU!
5. I prefer to have some sort of voice-over, but I don't care if there's a facecam. I tend to click away if there's no audio or just music, though.
I hope this helps! Good luck starting your channel!
