I wouldn't say I have one favourite youtube commentator as I enjoy watching quite a few channels, most notably are Dslyexci, FrankieonPC, JackFrags, PsiSyndicate and such. ToatalBiscuit is definitely up there as well as I enjoy hearing his honest thoughts on games, especially when they're complete rubbish. A smaller youtuber I enjoy watching is WoodenPotatoes, he mainly deals with Guild Wars and Guild Wars 2 on his channel, it's easy to get caught up in his videos for a long time.