I’ve not seen Angela’s Ashes - what was Robert Carlyle like with an Limerick accent? Ireland is normally the test for someone who can manage many British accents with style.
Well, the Welsh can do anything perfectly, so it’s not surprising. 
What was wrong with his accent in The Prestige? Aside from sounding disturbingly like my Uncle Pete, it sounded pretty good to me.
Rachel Griffiths, Mel Gibson, and Russell Crowe have done some great and virtually flawless American dialects/accents from down under. It makes me wonder if there is some correlation dialectically that translates into an interchangeability and loss of accent between our two colonies’ version of English.
I don’t totally buy Hugh Laurie as House. The first time I heard it I wondered why he was talking like that. The roughness, some odd pitch qualities sometimes, and I think there’s a bit of a lisp sometimes which I’ve since heard in some other Hugh Laurie clips. It didn’t occur to me that he was British, but he sounded odd.
It’s usually that way; Xena never sounded like a British or Australian person, but it sounded like Lucy Lawless was trying to affect a deep, breathy sort of voice.
Yeah, James Marsters was good. In one episode Spike had to hide from someone and as a result did his idea of a British person doing a very bad American accent.
Speaking of accents, it turns out Gillian Anderson lived in England from 2 to 11. She later came here and developed an American accent, but now she’s back in England and is speaking with her English accent again. It’s very strange the first time you see it. There are some clips on Youtube; the Graham Norton interview is funny and dirty.
Harrison Ford did a great Russian accent in K-19: The Widowmaker.
Gwyneth Paltrow’s English accent in Sliding Doors was pretty convincing.
Well, Mel Gibson was born in the U.S. (Peekskill, NY) and lived there until he was 12 when the family moved back to Australia. Then by the time he did “Mad Max,” he had such a pronounced Aussie accent (as did the other actors) that all the voices were redubbed with American voices for the U.S. release. In 2000, it was re-released with the original Australian accents, and has since been released on DVD with both the Australian and U.S. soundtracks on separate tracks. Presumably Gibson spoke with a natural American accent during his childhood, and rediscovered it upon becoming a major box-office actor.
IME, many non-Brits think that everybody in the British Isles sounds the same except when you cross over some line in the map. Many non-Hispanics have the same notion about Spain; in this case, without map lines.
I was surprised to find out David Tennant (Dr Who) was Scottish.
It seems to me that about fifteen to twenty years ago acting schools and acting coaches decided to get serious about teaching accents. Before then I could usually tell when an actor was attempting an accent from another country (in the English-speaking world). Now it’s increasingly difficult. This is probably most noticeable among Australian actors. Clearly they are told, “Forget about trying to make a career just in Australia. You can’t ever be truly famous that way. You’ve got to learn to do a variety of American and British accents if you’re going to make it as an actor.”
Anthony La Paglia and Judy Davis are the oddest of the Australian actors doing American accents. They don’t do standard American accents. La Paglia does this Italian-American New Yorker accent for all his roles now. Judy Davis has the character of a brittle New York intellectual that she’s done for a number of movies, including several for Woody Allen.
Toni Collette, who played the mother in The Sixth Sense, shocked the hell out of me on the DVD extras when she was speaking in her normal Australian accent. I saw her in Velvet Goldmine, too, which was an awful movie, but Collette’s character went back and forth between American and British accents seamlessly.
I think Tracey Ullman does various accents pretty well.
Whoa, whoa, whoa, back that train up. MEL GIBSON? I like a lot of his work but he sounds as Australian as a kangaroo in a billabong whenever he tries to do an American accent. (The irony being that Mel Gibson is, in fact, American by birth. Same with Nicole Kidman.)
The only movie I’ve seen him in where you couldn’t tell he was Australian was “Braveheart,” where it was masked by his Scots affectation.
Kevin Pollak is one of the best ever in terms of impersonations and accents. He doesn’t use these talents very much in the movies, but his standup act is incredible. I saw him perform a couple of years ago. His English accent is impeccable. A few years ago he was in England, listening to the news there. He talked about how their news announcers speak in such a way that their voices go “down at the end.” His vocal intonations were spot on.
He can imitate Simon Cowell perfectly. He also does Columbo, Schwarzenneger, Christopher Walken & William Shatner to a T. Pollak is an amazing iimpersonator.
I realize this isn’t exactly about accents, but Pollak deserves a mention.
As that big gal said on one of the roasts…Pollak does impressions of Shatner, Schwarzenegger, Nicholson- all the hard ones 
Sarcasm, it’s such an art form. It takes a real genius IQ
Yes, but she’s also responsible for the hilariously bad, I’m-ready-to-go-hang-out-with-Boris-Badinov Russian accent in Goldeneye. Remember? She was the crappy cabaret singer doing “Stand By Your Man.”
Her character in that movie should have hooked up with John Malkovich’s character in Rounders. Two worst Russian accents I ever heard.
Why would he do this? I think he’s a great actor, but maintaining the affected accent during interviews and such strikes me as a tad self-important and arrogant.
Anyhow, I think Cate Blanchett is completely believable in all character accents.
I thought Kate Winslet did a flawless american accent in Eternal Sunshine of the Spotless Mind.
The chubby little fellow from Little Britain (I think he’s Matt Lucas) pulls off a good accent from time to time. He once did a skit as a guy who looked and dressed identically to Mr. T, but claimed never to have heard of Mr. T. As I recall, his accent was a flat neutral North American. He wasn’t doing Mr. T, he was just doing… an unassuming guy who’d never heard of Mr. T. It was hilarious. He also did a good recovering Scottish drug addict, and a bunch of other accents. According to Lucas himself, however, he was criticized for his Welsh accent.