What puts me off Redford and Newman is while they are photogenic I find that as actors you could replace them with cardboard cutouts, for me. Just find them both rather dead behind the eyes somehow.
Gregory Peck and Cary Grant I thought were gorgeous in their day. Cary Grant was more twinkly than a box of Christmas lights.
Not a lot of these mentioned here do a lot for me, they are good looking but meh.