For male lead I pick Anthony Hopkins, his many films and diverse roles earn him greatest male lead of all times.
His over 97 films include the chilling Hannibal Lecter from silence of the lambs and a powerful portrail as the father in Legends of the Fall.
For female lead I have to step backwards into time, Katherine Hepburn is by far the greatest female actor of all times, she could handle comedy and drama with equal flair.
Katherine is the only 4 times Oscar winner . She made over 50 films.