Arguello and Louis for me. Some guys that havent been mentioned Schmeling & JMM..the things he did with his left hand were pretty amazing.
I think it probably has a lot to do with most people being right handed. More co-ordination and what not.
What I was getting at has more to do with it being easier to land a good left hook than it is to land a straight right hand. Left hooks are a much shorter punch that is harder to defend against. Very rarely at the highest level do you see fighters lead with a straight right. It is almost always behind a jab or countering a left hand shot by the opponent making accuracy more important for the right hand than the left hook.
Joe Louis, of course, Arguello, Floyd and Julian Jackson were the first that came to mind. Fighters who were very much about technique and maintaining their own 'proper form,' even though they all had different styles.