I have about 3&1/2 to 4 bookshelves filled with around 700 games by my last estimate. I used to have over 1,000 games but over the years I've sold off a lot of them.
I came to the realization that even if I sat down to play every game in my collection I'd probably die of old age before ever getting to them all! So, I started to reevaluate why the hell I was spending so much time and money on, what in essence was, storing things I would never even get to properly enjoy! Thus I started whittling down my collection to only games I thought were really worth keeping.
I've still got awhile to go, and I used to have to fight the urge not impulse buy from time to time, but I decided a couple of years ago to inverse the usual gamer attitude. Instead of immediately buying games, when they first come out at full price, playing them for like a week or so until the newness wears off, and then obsessing on the next big game/console, only to repeat the process over and over again, I decided to turn my gaze backwards. Not by becoming OCD about collecting retro games, but rather by enjoying what has already come before. By not caring so much about the newest thing or what I don't have, I realized I could better enjoy what I do have. In so doing I've removed a lot of the OCD inherent in collecting.
I wait for current gen AAA games to drop to >/= $20, while sticking to a strict list of retro & modern games that pass a certain threshold of quality before they can enter into my collection. Sometimes I wanna give a game a chance but I know all too well what it just leads to. This mindset requires patience and discipline for a collector. I know there will be a lot that I'll miss out on, but the same could be said of a lot of things. I can't spend my whole life collecting. What's the point in that and what purpose would that ultimately serve?