CANADA
First off is a popular North American civ that seems more in place in a Civ game than ever, since we now have another American colonial civ like Brazil as well as the US in Civ 5.
The most popular mod adding Canada to the game
is by TPangolin.
Here is a list of popular choices for leaders used in various incarnations of Civ mods. Keep in mind I might get some things wrong, as I am not Canadian and don't have as good a grasp on Canadian history as many would have.
John MacDonald: The first Prime Minister of Canada, and helped create the Canadian nation despite a lot of obstacles. However, as the founder of his nation, he does not seem to be held in as high regard as founding fathers of other nations, such as George Washington, Simón Bolivar or even Henry Parkes. This might be due to MacDonald's shortcomings as a human being, but people outside of Canada don't tend to recognize his importance, even among Canadian Prime Ministers go.
Finding a voice for Canadian PM's should generally not be hard, as there are several Civ players (some of them LPers) from Ontario, which is where the definitive Canadian accent is from. It might not be MacDonald's exact accent - he was born in Scotland and moved to Kingston as a boy in the late 1800's, but I think an Ontario accent would be recognizably Canadian to most people.
Lester Pearson: TPangolin makes a great case for him, citing him as "a war veteran, Nobel Peace Prize winner, respected leader and diplomatic superhero." He is regarded as one of Canada's Best Prime Ministers to the point that Toronto's main airport is named after him. His reputation as a diplomat and a peacekeeper makes him a great fit not only for TPangolin's "Keeper of the Peace" UA but also for Canada's reputation as a nation friendly to all.
Voice acting would be the same as with Pearson, probably even more relevant, since we do know that Pearson lived in Ontario his whole life and lived in the twentieth century. Better yet, we know what he sounded like, so we know what voice to aim for.
However, there is one leader choice that has his own strengths as a representative of the Maple Leaf Nation and might be a better one in some aspects...
Pierre Trudeau: Definitely a leader with a great personality and that dominated Canadian politics. Also recognized as one of Canada's greatest Prime Ministers. The main asset in his favor is that he is not only synonumous with the Canadian identity, but that he represents French Canada as well as he does English Canada, due to being a French-Canadian (which distinguishes him from US leaders somewhat) sympathetic with English Canadians and defender of an united Canada. Civ players are also familiar with him as a Canadian leader already due to bernie14's excellent Civ 4 leaderhead.
Finding a voice for him might be a little tougher since he is a French Canadian. While he would mainly speak English, he would probably have some sprinklings of French in his speech. (I particularly picture him saying "En mangez" which is a minced version of a quote he delivered to a bunch of Quebec postal workers, or perhaps even "fuddle-duddle" to someone that he hates.) A speaker from Montréal wouldn't be a bad idea as many of them seem to be bilingual anyways.
Anyway that is my two cents. What are the Civ community's thoughts on Canadian leaders?