A lot of fantastic ones I've seen in this thread before so I won't mention them but I'll mention a few Doom ones if anyone's interested in that:
First there's decino:
https://www.youtube.com/channel/UCJ8V9aiz50m6NVn0ix5v8RQ
He is a really chill guy who makes mostly videos on the old Doom games, and very informative ones at that, and he's very skilled at it too. Recently he's hosted a cloud-based server for the multiplayer source port called Odamex and did a few WADs with over 100+ players playing at once on the same server.
Then there's Aquarius199:
https://www.youtube.com/user/Aquarius199
He plays a lot of Terrywads/Trollwads and Jokewads, which are mods and maps for the old Doom games that either start out feeling serious then a trap in the end is put in to fuck with you, among exceptional cutscenes and overall shitposty shit, and gives his opinion on them, usually through text because he tried doing a facecam and let's just say it was a disaster haha. He's played a lot of my wads and all around he's a really nice guy.
ICARUSLIV3S:
https://www.youtube.com/user/ICARUSLIV3S/videos
On the opposite end of Aquarius199, this guy reviews the normie Doom mods and stuff and they're all usually really good stuff. He's done some videos on Quake 1 and Duke Nukem 3D shit too.
Zero Master:
https://www.youtube.com/channel/UCiVZWY9LmrJFOg3hWGjyBbw
Fantastic speedrunner of the old Doom games who knows the game mostly inside out and has found many ways to complete all the different challenges for it assigned by the community and whatnot.
Dwars:
https://www.youtube.com/channel/UCpYnXdkqC3aMyeg8ZDdBKag/videos
Dwars is a very informative classic Doom player who's made a lot of good playthroughs, has made videos comparing source ports for the old Doom games.
Now for some non-Doom ones:
Werster:
https://www.youtube.com/watch?v=FfbQDP2X4QE&list=PLKdCHbtiZdhCgRAQ0mEH0rBcskAoCD8uw (Showing this playlist, it's his best moments)
Australian Pokemon and Sonic speedrunner who is a very bright guy and knows his shit about the two games, he's held world records numerous times for the games and he's known for being very vulgar and also very rude but lovable (told me to kill myself once over a dumb comment I made in his stream's chat lmao) and is very open about his opinion about things such as the proper way to eat vanilla ice cream.
PhilsComputerLab:
https://www.youtube.com/user/philscomputerlab
This guy like LGR, 8-bit Guy, and such talks about old hardware and stuff as well. He has a very relaxing voice and is very informative.
My Life in Gaming:
https://www.youtube.com/user/mylifeingaming
This channel has extremely informative videos about retro gaming equipment, ways to get better picture and video and audio quality from your old game consoles, videos about playing retro consoles on modern TVs, FPGA (Field Programmable Gate Array) consoles that simulate the hardware of old game consoles and many more.
Tourettes Guy:
https://www.youtube.com/user/waynebarnhart
A living meme and internet legend that's been drinking up a stupor and cursing up a storm since the early aughties, him and his friends have had a website for their videos and eventually moved all of their shit to YouTube. 'Danny' supposedly died in 2008, but came back in 2009, as it turns out, the actor for the main character in it 'Danny,' Anthony Six got arrested for speeding.
The Angry Grandpa Show:
https://www.youtube.com/user/TheAngryGrandpaShow/videos
He unfortunately passed away, but it's all an archive of what was a hilarious and awesome man with anger issues known as Charlie Green, widely known as The Angry Grandpa.
There's too many amazing YouTubers for me to even list or count here, but these are/were some of my favorites. I've been on YouTube since 2006/2007 around and I've seen many come and go. I genuinely hope COPPA and all this other shit that's going on doesn't fuck up everything.