These are something I will later start myself (Still trying to fix that commentary of mine when I have time.), but I thought I should list some good channels here if you haven't seen any before. Since surprisingly many haven't and might find them interesting.
What are these Let's Plays anyway?
Well, Let's Play or just LP, is a walkthrough of a game that includes commentary. These started on the forums of the comedy website Something Awful in 2006 and rather quickly became popular on sites like Youtube. During those times they still weren't in video form however. Players would just take screenshots of their gameplay and add annotations to them. Michael "Slowbeef" Sawyer is usually credited as the pioneer of LPing, but is probably even more known for his review videos for LPs and the like with Ben "Diabetus" Whitfield.
If you have any other Let's Players yourself who I haven't listed here, feel free to add them as well. There are tons after all.
Chuggaaconroy - Classic console LPs with a heavy focus on Mario. One of the first and most famous LP producers on YouTube.
NintendoCapriSun - Heavy focus on Nintendo games. Huge fanbase as well.
ProtonJonSA - Another LPer who prefers older games. Also well-known in the community.
HCBailly - For me mainly known as the best Final Fantasy player of all time. Has a lot of information about the games he plays and always has something funny to say while being informative.
superskarmory - Focuses on Pokemon games. Very informative LPs. Also has his own forums:
[You must be registered and logged in to see this link.]TheRunawayGuys - Collab channel of ProtonJon, NintendoCapriSun and Chuggaaconroy. Sometimes have they special guests taking part in their LPs. Some of the funniest videos I've seen.