Tarmack
Rhetorical Porcupine
I ask them to comment about something relevant to my video,
e.g. I made a cooking video, so I asked them to comment what I should cook next. I made a video about things to do when you are bored, so I asked them what stuff they do when they are bored.
But my channel isn't big, so I don't get many comments, but when I do, they are nice
You should try to be more specific. One thing that people genuinely don't respond well to is too many options. If you ask them what you should cook next, their brain will often disregard the question because you have asked something too general with too many possible answers.
Now, if you turn around and say "Today we cooked X, I've been debating between cooking Y and Z next. I'll leave that decision up to the viewers". Then you include an end-card with an image of Y and Z, whatever those foods are. And you tell the viewer again as soon as the end-card is displayed to tell you in the comments which of the two they want to see you cook next. (or you can get clever and use annotations with bit.ly links to measure click votes).