Purchased this without paying attention to the hardware requirements. Seems I need a new GPU to run it. Oh, well, my machine is getting a little dated. According to Moore's Law, this machine is four or five generations out of date.
Cities: Skylines is also a major memory user. My 8 Gg is running 60-70% used and it requires a page file. I know this latter because when I put a solid state drive in my computer as C: I turned off the page file. The game would crash after a few hours of playing. The solution was to have Windows create the page file on the HDD. I wouldn't want to try running it on 4 Gg.
Knowing that you are an SC4 aficionado, Nonny, it might be worth getting a new card for this game. Mine is an Nvidia GTX 650--pretty low end and now 1 1/2 generations out of date, but it works fine for Cities: Skylines, so a new AMD or Nvidia in the $150-250 CDN range would be more than enough. A few SC4 veteran modders are starting to do some quality stuff, though the current mod and "assets" (C:S's term for buildings and lots) offering is up and down. Steam workshop doesn't have the same quality filters that veteran SC4 sites like Simtropolis, SC4 Devotion and SimPeg have, so there is some junk out there, but there are also some excellent mods and assets appearing, too. This game could be the successor to SC4 if the developers keep at it and the modding quality continues to rise.