From my personal experience:
Worst by a long shot .... BSA, Tasco and Simmons. I will never spend $1 on any of their products.
As for flat out best? Zeiss , Swarovski and Kahles top of their lines are the best scopes I have, and in my opinion superb performers. And for what these cost retail, they should be !!
I have had several scopes whose performance fell in between these two extremes. All were in about the $300-$500 range MSRP .