Some of my favorite LPs have come from LtMkilla (Dead Space and the ill-fated Bioshock LPs come to mind). His humor probably isn't for everybody (whose is?), but I love his videos.
GeopLP's Assassin's Creed series is to me the gold standard in a lot of ways: http://www.youtube.com/user/GeopLP/videos?view=1&flow=grid
But people like different degrees of all that stuff - I generally find YogsCast to be too silly, but thousands of subscribers obviously disagree with me, and I'm sure there are Starcraft or LoL watchers who hate all the contextual strategic commentary that I find absolutely vital in those videos. Similarly, different people and different formats like differing amounts of audience participation - I usually watch stuff on YouTube or Twitch weeks after it was recorded, so Q&Aing with your chatroom means I'm missing half the conversation, but for guys watching it live that's pretty awesome.
I personally fancy to watch episodes of FAF (Supreme Commander - Forged Alliance Forever) episodes on YouTube, just because the game is so good. I have nowhere near enough time to play to get to that level of proficiency sadly and I prefer to play single player.
http://en.wikipedia.org/wiki/Electronic_sports http://www.youtube.com/results?search_query=faf
I stopped playing after awhile because it started to feel more like a job and less like a game.
This is the crowd - http://cdn0.sbnation.com/assets/3517059/league_of_legends_wo...
IMHO this is beginning to rival professional sports tournaments in every way possible. The viewer count (couple hundred thousand) might not me a lot compared to football, but is still pretty significant :)