As a blanket answer I would suggest searching titles by release date and look around for older stuff. You can always check minimum specs as well, for things you are interested in.
Another nice way to find great titles is to do a search on "best pc games of all time" and you will start to see common titles.
For older systems, and not saying these will all work but:
Tom Clancy Advanced Warfighter series
Crysis
Call of Duty
Hitman
Many of the turn based strategy games would work like Civilization, Warhammer, Command and Conquer, Warcraft
even modern simple titles could work
EDIT- It is VERY important that you use a service, like Steam for instance, when trying to play these older titles. For the most part anything that is on Steam is going to work and had all the patches and updates such that it CAN work on an OS it wasn't designed for. Be very cautious to going to 'certain' sites that offer to sell game CD/key really cheap. It isn't that they are bad, per se...but for instance Civ 3 doesn't natively work in Win 10...unless you open it in Steam...