The channel that got me hooked was AgentJayZ. AgentJayZ, whose real name is AgentJayZ, is a gas turbine technician with S&S Turbine Services[c] and Jet City Turbines stationed in Fort St John, British Columbia, Canada.
It is immediately obvious that Jay is very knowledgeable and takes great pride in his work; but what makes this Youtube channel a gem is his ability to explain the nitty-gritty of how turbine engines work. If you've ever been curious about how a jet airliner pulls its massive bulk off the ground and into the air, I can recommend the playlist Your questions answered[d].
As someone born in 1978 I grew up on Carl Sagan's Cosmos. While I don't actually remember much of the TV-series, I do remember coming to kindergarten one morning and excitedly telling my friends that the day on Venus was longer than the year. At a much more advanced age I got hooked on Kerbal Space Program; so apparently the seed that was planted did grow.
Cosmos was popular science, which by its nature is a simplified and somewhat adjusted version of science. In order to cover enough about the subject, and still be something five-year-olds can grasp at least somewhat, trade-offs must be made. Deep Sky Videos is still popular science, but for grownups. The subject matter is more advanced, and it doesn't have the meditative tone of Cosmos, but even though this is the "hard nose of science" there is no mistaking the radiant enthusiasm that the lecturers bring.
In particular there are two who stand out for me: First in alphabetical order, Dr Meghan Gray[f], who studies galaxies and other big stuff out there such as the large-scale structure of the universe. I can't think of a single video with her that haven't made me think "wow I didn't know that but it's awesome".
Second, Professor Michael Merrifield[g], who specializes in galaxy formation. Many times I've found myself on the couch, excitedly listening to him enthusiastically talking about galaxy radiation, pulsating stars and other amazing objects; or having Dave Parker's play list of his videos[h] playing in the background while working.
Both bring a fantastic ability to rapidly distill very complex concepts to their essence and communicate that in an understandable and clear way.