What are "Good" and "Great" Conversions

I was realizing that I’m tracking conversions but have no idea what “good conversions” are.

1. What is a good email open rate?
2. What is a good conversion of sales off of a 3 part video series?
3. Is there a good open rate on sales pages?

My goal this year is to know my numbers, but it’s good to know what industry norms are so I know if I’m a great range or not 🙂