Here are the fights I rate as the best/biggest wins for the Klitschko's

Wlad: Sam Peter, Ruslan Chagaev (1st person to stop him), Chris Byrd X 2, Calvin Brock(1st person to stop him), Tony Thompson (1st person to stop him)

Vitali: Cris Arreola (1st person to stop him), Corrie Sanders, Sam Peter(1st person to stop him), Danny Williams

....if Ruiz would fit on anyone's top 3 it would have to be Vitali, because before fighting Lewis Vitali didn't have any top teir fighters on his record outside of Chris Byrd. The guys Wlad fought (that I listed) were all tough, they had awkward styles or big power and he wiped the floor with all of them.