I'm graduating from McGill and going to Harvard for grad school, so maybe my perspective can be helpful. I don't think the two schools are even remotely comparable, and neither does anybody else who goes here. People only say "The Harvard of Canada" to make fun of ourselves, I've never met anybody who believes it. I wouldn't say we're the Ohio State of Canada either, but maybe the Michigan of Canada. McGill is a perfectly strong public research university, but it doesn't have anything approaching the resources, selectivity, or status of a school like Harvard.
It's a good place to go if you want access to high-quality research and don't mind a large and relatively impersonal undergraduate experience. I've enjoyed my time here and I would make the same choice again given the chance, but let's accept the school for what it is: a great deal for a strong education and an important public resource. Rankings seem to place McGill anywhere from 20-70 in the world, but these tend to favour large, research-intensive schools anyway. QS puts McGill at 21 and Brown at 52. Would I advise people to choose McGill over Brown? Not in any circumstances I can think of.
UofT and UBC are both better than McGill at certain things and worse at others. The 1/2/3 ranking will depend on your priorities, but in terms of research I think UofT is probably stronger in the most areas. They're all relatively similar schools in terms of quality and environment.