Who does it best? Who stinks? I just started watching the Walking Dead and was very surprised to learn Andrew Lincoln who plays the lead is English. Gary Oldman is great. Russell Crow does a good job. I'm a big fan of Hugh Laurie but I thought his accent on House wasn't very good.
Cary Elwes (Princes Bride, etc.), Damian Lewis (Homeland, Band of Brothers), Dominic West (The Wire) and a couple of other actors in The Walking Dead are also Brits. Also the actor playing Lee Adama in Battlestar Galactica. Frasier's dad - also British. Sadly in that series Daphne's British accent was terrible despite the actress being British!