There are also some top tier speed runners, professional gamers, and industry people that stream or contribute to streams. I only watch people that can play at an 'A' level or can contribute an interesting dialog. Plus points if you know a tremendous hell of a lot about the game you are streaming, or can discuss trivia, tactics, or sekret info for the game.
The streamers that get popular enough to make meaningful income through streaming are the ones that can manage a show. Meaning you should be spending more time in prep work, set up, and planning than you do putting your stupid looking face on the interweb. If you think you can make money at this because you own a shitty ass webcam, mic, crusty couch, ps4, and Diablo3, well, that shit better be Hardcore.
Some of the Twitch streamers I watch that can occasionally put together a decent show:
CobaltStreak, Richard_Hammer: Nightly deathless Binding of Isaac speed runs. Organized and live streamed a Binding of Isaac competition.
LethalFrag: neckbeard that streams rogue style games - FTL and SotS
Adam_Ak: props for Doom speed runs! but mostly known for GTA speed runs.
DansGaming: The geriatric porn of the game streaming world. Guy spent over 2 weeks going through every mod and texture patch tweaking settings for Skyrim to get the best possible look and performance for that engine before streaming. Something I will never do myself.
Then there are guys like Towellie, that stream WoW raids, that I put on whenever I feel the urge to play an mmo, to remind myself why I don't.