games? it depends on where you have them installed. and whether they use the registry... more often than not you will have to re-install them.
as for personal files they mean user created data like save games, video and pictures which all tend to end up in the c:user folder unless you change there user paths.
when i upgraded from windows 7 last year all my games and data seemed to be there and all were usable without having to re-install but for the most part i install my games on a secondary drive so that may be the reason i had so little in the way of issues.
resetting windows 10? if you have 10 installed already resetting it wont do much, if your just looking to repair some corrupted fines than sfc/scannow from an elevated comand prompt would be a quicker option(along with clearing out old reg entries with something like ccleaner). the only real reason to run the installer again is if you completely broke the master boot record or some other similar disaster.
so before you start plz explain why you want to reset windows.