Hmm, let's see:
OD&D (2nd printing blueish monochrome book)
OD&D (BECMI and Rules Cyclopedia)
AD&D 1
AD&D 2
D&D 3.0
D&D 3.5
Shadowrun 1st/2nd
Gamma World 3
Gamma World 4
Top Secret
Top Secret/S.I. (complete body of work)
James Bond 007
Spycraft (everything except the1960's book and The Agency)
Star Frontiers (complete body of work)
Star Wars d6
Star Wars d20
TORG (complete body of work, including all Infiniverse newsletters)
Paranoia
Twilight:2000 v1
Twilight:2000 v2
Twilight:2000 v2.2
Marvel Super Heroes (TSR original Basic/Advanced)
DC Heroes (Mayfair)
Lords of Creation (complete body of work)
Call of Cthulhu BRP
Call of Cthulhu d20
Vampire (first edition)
Rolemaster
Harn (3rd edition, its a free pdf - so I don't know if it counts)
Buck Rogers: XXVC
Dangerous Journeys
Delta Force
Ghostbusters/Ghostbusters International
I'm sure I'm missing a game or two from this list.
This doesn't include all of the various add-on "campaign settings" I have:
Greyhawk (boxed set, Greyhawk Adventures Book, From the Ashes, City of Greyhawk boxed set)
Forgotten Realms (1ed, FRA Book, 2ed, 3ed)
Myth Drannor Boxed Set
Lankhmar (1st edition)
Undermountain I/II
Spelljammer
OD&D Wrath of the Immortals
OD&D Dawn of the Emperors
Dragonlance (Dragonlance Adventures Book, Time of the Dragon/Taladas)
Ravenloft (1ed)
Dark Sun (1ed)
Menzoberranzan (even though it's just a city setting)
Maztica
Kara-Tur
Al-Qadim
City System (1ed Waterdeep campaign set - the maps take up two 34x44 plotter sheet/ANSI E sized pages...)
About 1/2 of the OD&D Gazetteers
Hollow World
Shadowforce Archer (all books)