How do I see which products are selling, and the quantities?

How do I see which products are selling, and the quantities?

Is there a view or a report that I can make to analyse which products are selling? We need to know which products are our best sellers/worst sellers and whether it's worth to continue selling them. We like to review this quarterly and annually.
For example, if a certain colour of a product doesn't sell at all in two years, then we will discontinue it. 

I am a CRM Professional Edition user, small 2 person company.

This seems like a fairly normal business requirement… any ideas?