Virtually all of the 407 is surfaced in concrete. From the 403 in Mississauga to Markham Road in Markham.
The 427 is slowly being surfaced in asphalt, but both the northbound and southbound collector lanes are still surfaced in concrete.
This is the 427 from 2005:
Ontario has had a long history with concrete highways. These photos were taken in 1989 from the Vintage King's Highway website, and are of the 401 through Scarborough, while it was still surfaced in concrete:
Other highways outside of the GTA are surfaced in concrete as well. This is the 115:
I do agree, however, that there is more concrete in Windsor than there is in the rest of the province.