I've found that I've never really watched a Let's Player to sit and watch a game. I leave that for trailers, a few reviews, and my own hands on experience. I tend to watch 3 kinds of streamers:

-Friends streams because I get a chance to talk with them in the chat and maybe help them in a game if they're stuck.

-People who have interesting commentary about the gameplay footage, maybe some behind the scenes or making-of type of information.

-YouTubers I enjoy watching otherwise. Often times these aren't even video game centered channels, but they open up a relaxed environment where they participate in Q&A while playing games as a sort of backdrop.

The actual watching of the game is the least compelling thing for me, unless I'm feeling nostalgic or doing article research, in which case I'll find an archived Let's Play on YouTube. What do you look for in a Let's Player?