I'd say that Toronto has become dirtier, though it's not a particularly dirty city overall. Mostly a combination of increased population in the central city, small (but noticeable) cuts to general services and a significant influx of homeless in certain areas. The city has gotten better at the upkeep of some public spaces, but you'll see large piles of garbage in secluded areas such as under overpasses.
Compared to when I first visited 3 years ago, Johannesburg has gotten quite a bit cleaner, although it's a very dirty city overall. Service delivery in central areas has improved but it's not enough to keep up with high density, particularly in proximity to hijacked buildings. Areas near informal settlements are also quite bad, though the city is trying to expand waste collection in these areas (how effective this is I couldn't say). There's also been a push for community cleanups in parks and such, which started before the recent "trashtag" challenge. It's made a noticeable difference for parks in middle-class suburbs and stable parts of the inner city.
Another big issue is illegal dumping, particularly from construction projects and renovations. A lot of contractors find it cheaper to risk fines and just drive to an isolated area to dump waste. I've seen roads just outside the urban area that are lined with piles of construction waste - you can actually make them out on google maps pretty clearly:
https://goo.gl/maps/QGQcmaiUjxHoC2s79
On the whole I find South African's have completely normalized public littering in a way that completely crosses class / racial lines. I see new garbage on the sidewalks and in the local park walking to the gym every morning and have seen people just throw stuff out the windows of very expensive vehicles. Hopefully that culture can be changed over time.