As he becomes joint number 1 bowler in the world with Murali
Rankings here as we salute Dan Vettori as the no.1 ODI bowler
There you go. I'm not sure how much notice you take in them or not, but by just watching cricket alone (forget stats etc.) and in particular the Australian cricket summer, you would say Brett Lee is the best fast bowler in the world in both forms. If he isn't then he did bowl pretty darn well IMO.
So it is official Dale Steyn > Brett Lee in the rankings but by watching cricket live Lee > everybody else.