I don't. According to GOG I own 835 titles (thanks bundles! and recently Epic), a big chunk of it I will never touch, a big chunk I am somewhat interested in but am unlikely to get to, many games I played, enjoyed and am unlikely to get back to, some games I played and might play again, some games I will play.
I use tags on gog (and previously steam) to remember games I might return to (tagged as "classics to be returned to") and tag games I am interested in ("to be played").
On a side note, I wish I could erase my memory and play through Witcher 3 again.