I lived by Yonge and Steeles for about a year. Sanction was really close by and York (alma mater), but not a lot of skate spots and not much to do. Closest park at that time was Cummer haha. The York campus had a few spots, though. Pretty sure it's undergone a fair amount of reconstruction so it's probably even more skateable.
Didn't spend lots of time in Burlington, Mississauga, Oakville, etc. but they seemed like nice places. Mississauga in particular seemed really good for skating; I worked as a TV/movie extra for a bit and saw some nice spots whenever we'd have a shoot in 'Sauga.
I think the insta account @wintercrimes is documenting spots in Toronto and in the GTA as well.
Edit: Also, I've seen pics of a really nice park somewhere in the GTA, it's fairly new, can't remember where exactly....