Ontario's route numbering system is fine.
I get the appeal of the US numbering system, and that of Quebec's system, but there isn't much of a benefit in Ontario.
Consider Buffalo:
The freeways in Buffalo can include interstate routes, US, route as well as state routes. Aside from the interstates, there are both US route and state route freeways that are important routes throughout the system, so the route hierarchy of both what the route number and the shape of its shield breaks down pretty quickly there too. Just driving he routes, who would figure that Route 33 is in fact a higher order route than the lower numbered Route 5. Same with US Routes, US-219 is an important efficient route for through traffic. US-62 is a useless holdover from before the interstate era. When you think about it, that doesn't really make sense even though anyone familiar with driving through Buffalo (as I am) has rationalized it.