I tend to like channels that make reviews of older gen games. If you haven't dived into these kinds of channels, what is cool about them is that they are invariably interested in games beyond just the biggest and most well remembered. Snesdrunk, DariaPlaysRPGs, and AboveUp are a few that I've been subscribed to for a while. Salokin is a new channel that I've subscribed recently.
Snesdrunk is rather well known and has loads of SNES videos. He likes making his videos short, to the point, aiming to deliver good information and a sense of if it is worth your time compared to other similar games. He also does videos on other retro systems, including Sega Genesis, Arcade, and NES.
Daria focuses on on 8 and 16 bit RPGs, which sometimes just broadly includes games with fantasy/medieval aesthetics and box art. Much more of a focus on Sega Genesis and NES though. She seems to enjoy making videos on unpopular games and obscure titles that otherwise fit the channel aesthetic.
AboveUp tends to cover Japanese games, with no specific system or era although he seems to like series from the PS1, PS2, and Falcom games.
Salokin does PC games, usually ones involving shooting like FPSes, TPSes, or vehicle/mech games. Lots of early 2000s games, although it isn't limited to a specific era.
I find analysis/essay/topic channels interesting to dip into but disappointing to subscribe and put into my feed. Here's a few though:
Matthewmatosis' channel is very well known, but should be highly recommended by someone here.
Psych of play (aka Daryl Talks Games) has a very clear focus: psychology research and concepts applied to the player and game design. I'm guessing he is a relatively young psychology graduate. The video presentation often has an overt interest in catching an internet audience, but the subject can be interesting on its own.
Gamedenker does analysis/topics videos. There is a unique approach to this channel, which roughly can be described as starting from art, philosophy, and books and then trying to tie a discussion there to games. A video where Nassim Taleb or Plato is the framing device for a topic video would be an example. The videos don't come out often and have lovely production values to them. It's clearly more of a passion channel for the two women doing it.