Robert Mitchum is up there, but no one can touch Cary Grant for me. I may not care for all of his films, but he's great in every one of 'em! That said, Robert Mitchum is incredibly underrated. And I have a magic 3 from the Pre-code era: Ricardo Cortez, Lyle Talbot & David Manners. I watch anything they're in!
And for the ladies, I'm pretty cliched...Joan, Bette & Stanwyck, from Pre-code all the way to the end! But there can be a big difference between actresses & performers. My all-time favorite female movie star is Rita Hayworth. In fact, I have a signed, numbered George Hurrell portrait of her. She's luminous, probably the most beautiful woman I've ever seen. And when she dances, she is either joy or sensuality personified...sometimes BOTH lol!
She. Is. A. Queen. Yassss!