-Without Sharingan I would still imagine Kakashi to be quite strong. For 1 his father was quite powerful, his master was the 4th Hokage and he was good friends with Jiraiya. He would last longer in fights b/c his chakra wouldn't be sapped away quickly. He would probably be more skilled b/c he wouldn't have to depend on that eye.
-IMO he had a lot of people around him that could have made him powerful if not for the sharingan. He could have personally trained under Jiraiya and such.
-There is even a slight chance that Minato would have taught him FTG.