They are so different that theres not much comparison. And both have lost a lot of their talent in their old age. At their peak i would say they are about on par, but nowadays i suppose Romero is a better director--i still think Bruiser and Land of the Dead were lousy but he directed them better than Lucas directed any of his prequels. I'm working on Diary of the Dead, which is shooting in Toronto right now, and the script so far is equally hit and miss...