It depends on what exactly do you like. I play .io games! It’s just a fun, relaxing and exciting experience that you will enjoy quite a lot. For example you can start with Scribble http://iospace.games/scribbleio and then to search some another variants.
As for me, the most interesting are online games like WoW, Eve online or http://www.muonline.us . As the best single player are at consoles, it's just my opinion. They has RDR 2, new Spiderman and so on. But PC allows you to explore almost infinite online worlds full of other people and that's just awesome \0/