I'm sure we've all watched films where an actor tried to pull off an accent and failed badly. See Robert Pattinson in Little Ashes if you haven't.
Failure to do a convincing accent can take you right out of the story and you end up becoming annoyed with the film. But what if they did it in their own accents? Could you overlook this detail or would this put you off?
I used to dislike Meryl Streep because all she seemed to do was accents. On the other hand, do you think Brando sounded anything like the real Mexican, Anthony Quinn, playing his brother in
Viva, Zapata? Brando was much better at a Southern accent and phrasing in
Sayonara. However, he didn't look or sound like the real Okinawans in
Tea House of the August Moon, although he did as much as he could with that role, better than Mickey Rooney's Japanese tenant in
Breakfast at Tiffany's.
Sometimes a bad accent can be fun, like betting whether Laurence Harvey will deliver his next line in his native British accent, a phoney Southern accent, or something entirely different in
The Alamo. Accents were about the only interesting thing in Coustner's
Robin Hood saga, where seemingly all of the "bad" guys were played by British actors with real British accents and all the "good" guys were Americans with American accents.
One of the worst accents of all time was Paul Newman's "Frito Bandito" rendition of the Mexican bandit in
The Outrage. It was so bad it even took attention away from another of Harvey's Russian roullete lapses between his British and a fake southern accent. Yet the movie is still interesting despite those lapses.
And then there were all those bands back during the "British invasion" who sang in American accents but their British accents when they talked were almost unintelligible. A Scot accent is particularly hard for me to understand despite frequent contact with Scots.
Basically, I'm all for a person who is good at accents doing accents, but it takes study and practice to do them well. Without that, they're better off just acting the foreign character without attempting a bad accent. For instance, in
Valdez Is Coming, Lancaster portrays a Mexican in an Anglo-dominated US of the late 19th century more through attitude than accent with deference, down-cast eyes, hat in hand in the first of the film, and later native pride and defiance and the experience of a man who conquered that land before it was part of the US.