* means I played or ran it
*D&D 3.X
*D&D 4e - core plus a few sourcebooks
numerous 3E sourcebooks both WOTC and third party
*CoC
*Delta Green - main, countdown, eyes only
at least 20 CoC books
*twilight 2000
*M&M 2nd edition - and first edition
*AFMBE
Promethean
*The entire Hunter the Reckoning line
Wraith plus 3 sourcebooks
*Mage oWoD
Dark Heresy
*a bunch of planescape boxed sets
warhammer fantasy roleplay - both editions
several boxes of bargain bin finds
*unknown armies
wild talents essential edition
*monsters and other childish things - entire line thus published
*prime time adventures
sorcerer
CoC d20
*Gurps 3rd edition
*GURPS 4th edition
Fading Suns
*Scion - hero only
*Fates Worse than Death - actually ran this crazy fucking game - things a phonebook packed with all kinds of neat shit
WORLD OF SYNNIBARR
*Reign
*Colonial Gothic
Cthulhu Live
Dozens of Dungeon and Dragon back issues
Mutant City Blues
*Fear Itself
*Esoterrorists
Trail of Cthulhu
Alpha Omega
Dogs in the Vineyard
*Some assorted palladium books - prolly at least Heroes Unlimited and the rifts corebook I might still have Nightbane
Engel
True20
*d20 modern
SLA Industries
Tribe 8
Gear Krieg
Heavy Gear
Underground
*Dark Conspiracies
Chill
Inquisitor
Pandemonium
Conan - d20 mongoose version
Elric
*Paranoia
*Hackmaster - all the monster books plus a few others
Castles and Crusaders
Orpheus - entire product line
Changeling - oWoD
Marc Miller's Traveller
That's all I can find, not counting war games, board games, card games and the like. I also have a library of assorted academic, filmmaking, and esoteric books that I will not list here because this has already wasted enough of my time as is. There's a decent stack of various sourcebooks that I won't list either.
EDIT: more games added.