Left to right: Canadian flag, sugar maple, red maple.
I go with sugar maple based on the shape and the smooth margins, although one can certainly argue that the margin detail simply isn't shown in the flag. And of course there is a continuum of red and sugar maple leaf shapes. This link http://www.cbc.ca/newsinreview/may98/maple/canflag.htm
suggests that it's meant to be a generic maple leaf, so I guess the answer is all of the above.
The leaves definitely look like Sugar Maple, but the bark doesn't look like any Sugar Maple I've ever seen around these parts. The stingy bark almost looks like Silver Maple. Maybe they grow them different down in OH? Or could it be Norway Maple?