Actually, riding size in the current system is an interesting point of debate. I personally think that it's crazy that ridings, barring exceptional circumstances like vast remote northern regions, have any significant population difference at redistribution. The courts enforce this very tightly in the U.S., though they have other ways of rigging ridings which are rather worse than the situation up here. The Australian model is also worth following, in that it tries to take into account population growth so that ridings should all be roughly equally sized at the midpoint year of the redistribution.
Anyway, what's interesting to note is that Toronto is not at all underrepresented in our current system. In fact, the downtown Toronto ridings are some of the smallest in Ontario, and they're experiencing virtually no population growth either. There's a wide variation in the population of rural ridings. The people who really get screwed are fast-growing cities like Kitchener-Waterloo, and especially the 905 suburbs. Brampton West is absurdly large with 170,422 people (and growing unbelievably rapidly) at the 2006 census. Parkdale-High Park had 102,142 at last census and it's shrinking. By the next redistribution, which won't come until about 2013, Brampton West will probably have at least 250,000 people, while Parkdale-HP Beaches-East York, Toronto-Danforth, etc. will be well under 100,000.