I've narrowed my game collection down...dramatically....and it's been reduced, essentially, to the following titles and associated sourcebooks:
Dungeons & Dragons 5th edition (All WotC books and a selection of 3PP)
13th Age (all Pelgrane books and one 3PP)
Traveller (All Mongoose 2nd edition only, Traveller edition of Mindjammer)
Starfinder (almost everything so far released, and select 3PP)
Cypher System (All Cypher System and Numenera books plus The Strange and Vurt)
Genesys Core RPG (plus Realms of Terrinoth)
Pathfinder (Pocket Book Editions only!)
Call of Cthulhu (All 7th Edition and a select few earlier titles)
Delta Green (Well, this stuff is new, the Arc Dream edition which I am really enjoying right now)
Basic Roleplaying BGB
Cthulhu Dark Ages
Mythras (plus Monster Island and Classic Fantasy, but I'm debating about the value of the latter)
GURPS (all of whatever I still have, which is mostly 4th plus favorite 3rd edition books)
Savage Worlds (core plus genre books, and a couple sourcebooks I love like Tropicana, Zombacalypse and The Last Parsec)
Fantasy AGE (and assorted sourcebooks)
...that constitutes the sum total of "games I continue to own because I run them a lot." Or like to think I will soon.
I also have retained in my "collection" part of the collection the following books which I plan to read and maybe some day run:
Symbaroum (all books released)
Conan: Adventures in and Age Undreamed Of (All releases so far)
Infinity RPG (all books so far)
Unknown Armies (3 book box/screen set)
Robotech: The Shadow Chronicles Deluxe Edition
Mekton Z Reprint
Deluxe Tunnels & Trolls (and related recent releases; all my old stuff from the seventies and eighties has gone to a fine group of diehard collectors via ebay)
Metamorphosis Alpha (the hard to find one from SignalFire; I recently snagged it when I got hold of the producer of the game on his new KS to find out what happened to my copy)
...maybe one or two miscellaneous games I have missed.
But that's it. Depending on whether or not you're a major collector, that list will either sound anemic or immense. To me, this is very anemic, possibly the smallest I've kept my collection since 1995, when I mostly had a medley of AD&D 2nd edition, Call of Cthulhu and GURPS.
The new collection is missing pretty much all of my old OSR collection, which I sold off. As sad as I was to let some of it go, the truth is it was always more fun to read and explore than to actually do anything with. My key exception is White Star Galaxy Edition, but I didn't mind selling it for a very specific reason: the print edition on rpgnow is much higher quality than the cheap-o copy with thin paper and bleed through that I got through Lulu, so I plan to snag a nicer copy that way.
Another reason I got rid of some items is repetition. A lot of RPGs today, thanks to the OGL, tend to be variants of the same system. Most OSR titles are a result of this, and a lot of D100 system titles stem from the Legend OGL. Traveller has a similar (minor) problem of such nature with the Cepheus Engine (which come to think of it I do have in print, too). So a goal has been to reduce the amount of system redundancy in my collection. I still have a few areas where I could shave off a bit here and there. Luckily for D&D 5E, 13th Age, and Pathfinder despite their common ancestry I feel like each is distinct in its own right. But Mythras, Magic World, and BRP? An argument could be made.....and I've already cleared out all the other OGL-Legend derived homages and variants, including Legend itself (and yes that means I have decided to give up on OpenQuest, though I think it a worthy game, along with River of Heaven, M-Space, D10 Revolution and many other spinoffs from the Legend OGL).
I sometimes feel like as glorious as the OGL has been to promote hobby growth, some of that growth has been in a perverse, inward direction that stiffled innovation in the name of repetition.* I see it as a positive trend on the odd days, and a deleterious one on the even days, I guess.
But, I digress....
This grand plan to slim it all down does make me question why I am backing any further Kickstarters right now. Hmmm.
I'm still thinking of further ways to slice it down even more. For example, I almost never run modules. Ever. So why do I own so many for certain games? Things to think about.
*And the canonization of what amounts to a compendium of house rules or heartbreakers disguised as OGL variants.