A few years ago I realized I had almost 300 games on Steam that I never started or started and quit really quickly. I then installed all of them and said I wouldn't get a new game until I played and beat enough games to get under 100. I'm down to 120 - 130 unbeaten games.
I did break this rule a couple of times, and quite a few games were part of bundles, so I didn't count those as games I bought. But I've made a lot of progress.