Tom Cruise is only ever Tom Cruise to me. I don't like him anyway, not since I saw a pic of him grinning his face off as he and some female 'celeb' were holding up two little Siberian tiger cubs at some mega event in a theatre. I was outraged at their being used like that.
Some actors are just like that IMO - good actors or not, they don't truly 'become' whoever they're playing - not to me anyway. I still remember Robert Redford in Out of Africa - to me he was just Robert Redford right through.
Others, e.g. Meryl Streep, Al Pacino, to name just 2, most certainly do.