Which country has the most lakes?

Canada has over 3 million lakes . . . more than every other country in the world combined.

There are some two million lakes in Canada, covering about 7.6 percent of the Canadian landmass. The main lakes, in order of the surface area located in Canada (many large lakes are traversed by the Canada-U.S. border), are Huron, Great Bear, Superior, Great Slave, Winnipeg, Erie and Ontario. The largest lake situated entirely in Canada is Great Bear Lake (31,328 km2) in the Northwest Territories. The deepest lake is Great Slave Lake, N.W.T., 614 metres.

http://www.mobrien.com/about-canada.html

Canada by far has more lakes than any other country in the world and has a large amount of the world's freshwater.
https://en.wikipedia.org/wiki/Canada#Geography_and_climate

There is no accepted answer to the question: How many lakes are there in Canada? The best answer is that 31,752 lakes have an area of at least three square kilometres. These data were compiled by Environment Canada in 1973.
https://en.wikipedia.org/wiki/List_of_lakes_of_Canada
http://www.thecanadianencyclopedia.ca/en/article/lake/