I was blown away by Ben Kingsley playing Gandhi – the resemblance both in youth and old age was phenomenal
From all accounts, Val Kilmer was perfect as Jim Morrison (I haven’t seen The Doors, myself) Apparently he not only really looks the part, but performs the music perfectly.
I’ve seen other people in the role, but Paul Scofield still seems the perfect Thomas More in A Man for All Seasons, even resembling the man.
If you couldn’t get Boris Karloff to play the part of Jonathan Brewster in Arsenic and Old Lace (He played it on Broadway, and was unavailable for the filom version), would it be possible to do better than Raymond Massey?
Speaking of Boris Karloff, one of his lesser-knowmn roles was as Peter Cauchon in the onstage version of Jean Anhouilh’s The Lark/l’Alouette, about the trial of Joan of Arc. I would’ve loved to have seen him playing the part of Cauchon in George Bernard Shaw’s play about her, Saint Joan. He would have been perfect.
Stephen Fry as Oscar Wilde. Not just an uncanny physical resemblance, but in terms of sophistication and wit, he is the modern equivalent in every way.
Except that he was also the perfect Doc Holliday. Offscreen, Kilmer is definitely not my type. But he’s really an excellent actor who is able to lose himself in a role.
Also: Dan Ackroyd as Jack Webb (as Joe Friday) in Dragnet. I read somewhere that Harry Morgan got teary-eyed the first time he saw Dan’s impression of JW.
Also some more: David Carradine as Cole Younger in Long Riders.
Edit: forgot this one: Arnold Scharzenegger as a robot in The Terminator. Perfect casting.
Two actors that always struck me as born to play their parts:
Richard Chamberlin as Father de Bricassart in The Thorn Birds, and also as John Blackthorn in Shogun.
Pierce Brosnan as James Bond. Pity contractual obligations kept him from playing the role until he was almost too old. Also that the series had gotten so silly by that point.