The most important thing is to be good at the game. You could be the most boring soul on earth, but if you're on top 10 legend, people will watch you because they want to become good as well.
After that, it's just your personality. It helps to be relatable, but if people find you entertaining, they'll watch your stream regardless of which games you're playing. It's important to note that not everyone has the personality for streaming.
Outside of that, is the news/the insight you can share. It's best to back up your statements with past data and facts, but some people like it when you lean a certain way (while other don't).