Which ones?
Let's start from the beginning...
D&D --(Three Book plus all four supplements, ADD 1e, 2e, D&D 3e)
Tunnels and Trolls
Monsters! Monsters!
Metamorphosis Alpha (original, Amazing Engine, FFE version)
Gamma World (1e, 2e, 3e, 4e, Alternity, S&S)
The Fantasy Trip
Star Trek RPG (FASA)
Traveller (GDW Original, New Era, Mega Traveller)
2300AD
Space1889
Twilight 2000 (1e, 2.2e)
Daredevils
Space Opera
Other Suns
Aftermath
Flashing Blades
Flight of the Phoenix
Chivalry and Sorcery (1e,2e,3e)
Freedom Fighters
Bushido (1e,2e)
Psi-World
Merc
Villains and Vigilantes (1e,2e)
Superhero:2044
Boot Hill (1e,2e)
Gangbusters
Delta Force
K.A.B.A.L. (Bonus points to anybody who remembers this one!)
FTL:2448
Fringeworthy
Stalking the Night Fantastic (1e, 2e aka Bureau 13)
Morrow Project
Palladium Fantasy Roleplay
Warhammer RPG (1e)
Rifts
TMNT
Robotech
Beyond the Supernatural
Heroes Unlimited
GURPs (way too many!)
Call of Cthulhu (1e, 2e, 3e, 4e, 5e, D20)
Superworld
Worlds of Wonder
Ringworld
Runequest (1e, 2e, 3e)
Stormbringer
Man, Myth, and Magic
To Challenge Tomorrow
Justifiers (1e, 2e)
Domination
Mechanoids (Original three books, Rifts Supplement)
Recon (1e, Palladium version)
Vampire (1e, Revised)
Werewolf (Revised)
It Came From The Late, Late, Late, Show!
Nightlife (1e, 2e)
L5R (1e, 2e, D20)
7th Sea (1e, D20)
Albedo
Elfquest
Mutazoids (1e, 2e)
Wizards (Bakshi version by Whit Pub.)
SLA Industries (1e, 2e)
Tales of Gargahntir
Pirates of Dark Water (Not the freeware game!)
Shadowrun (1e, 2e, 3e)
EarthDawn (1e, 2e)
Mechwarrior
Legionnaire
Kult (1e, 2e, 3e)
Star Wars (D6, D20)
TORG
Indiana Jones (TSR)
Masterbook(Blood Shadows, Species, Tank Girl, MiB, Indiana Jones)
In Nomine
Paranoia (1e, 2e)
Mutant Chronicles
Judge Dredd (GW, Mongoose D20)
Ghostbusters (1e, G.B.I.)
Top Secret (1e, TS/SI)
Buck Rogers (25th Century, High Adventure Cliffhangers)
MetaScape
Conspiracy X
AFMBE
Buffy
Witchcraft
Armageddon
The End (1e, D20)
Blue Planet (1e, 2e)
Twilight Imperium
Feng Shui (Daedulus, Atlas)
HKAT (1e, 2e)
BESM (1e, 2e)
Cyberpunk (1e, 2020, CyberGeneration)
Rolemaster
Star Patrol (go Zocchi Games!)
Champions (1e, 2e, 3e, 4e, 5e)
DC Heroes (1e, 2e)
Underground
Underworld
Chill (1e, 2e)
Star Ace
Timemaster
Star Frontiers
I have a lot more, but I'll start having to open boxes, these are just off the top of my head and my game bookcase. I've been playing and collecting RPGs since 1975 so I do have way too many. I didn't bother including a lot of the D20 stuff or a lot of spin-off games I've got lurking around.