Gggmanlives: He almost exclusively reviews FPS games, almost entirely ones on the PC, but if your a fan of either PC gaming and/or FPS games his channel is a must to subscribe to. Very, very good reviews on games like Half Life, Quake, and many other classic FPS series.
NEScomplex: Sadly he rarely posts videos anymore, but he is still worth subscribing to for the excellent videos he makes on classic Nintendo games, Nintendo Power, and pretty much all things Nintendo.
F4m1LyGuy10: This channel isn't so much original content as it is this guy posting a ton of great video game soundtracks. If you're a fan of video game music this guy is worth subscribing to.