this is based on the Wikipedia timeline of RPGs. no doubt there are twenty times more than these examples in various languages and hidden in non-traditional publishing
(highlighted titles seem especially fascinating!)
Dungeons & Dragons - heroic fantasy
Boot Hill - wild west
Empire of the Petal Throne - novel science-fantasy
En Garde! - historical adventure
Tunnels & Trolls - heroic fantasy
Bunnies & Burrows - anthro, environmental
Knights of the Round Table - medieval low fantasy
Metamorphosis Alpha - science fiction (on a colony ship)
Monsters! Monsters! - heroic fantasy, role reversal
Starfaring - Star Trek-like
Arduin - heroic fantasy, highly adaptable
Chivalry & Sorcery - medieval real-world fantasy
Flash Gordon & The Warriors of Mongo - science fiction tie-in
The Realm of Yolmi - science fiction, partially apocalyptic (I think? but it has interstellar trading, too...)
Star Patrol - space opera
Space Quest - space opera
Superhero: 2044 - costumed heroes
Traveller - big science-fiction including trading and ship-to-ship battles
Advanced Dungeons & Dragons - the game
Bifrost - heroic fantasy. Might be interesting as early UK/Euro takes on anything originating in the US are always insane
Gamma World - post-apocalyptic science fiction (going on to inspire Fallout)
High Fantasy - heroic fantasy (I think if you want a lite version of AD & D, Tunnels & Trolls has far more support)
John Carter, Warlord of Mars - science fiction tie-in
Legacy - more of a supplement for modeling certain societies? must peek
RuneQuest - heroic fantasy
Starships & Spacemen - Star Trek-like
Star Trek - Adventure Gaming in the Final Frontier - really really Star Trek-like
What Price Glory? - heroic fantasy
Adventures in Fantasy - heroic fantasy (from original D & D co-creator)
Buccaneer - high-seas piracy
Bushido - heroic fantasy in magical Japan
Commando - apparently more of a military skirmish thing
Gangster! - prohibition urban Chicago hijinks (might be interesting in parallel to Shadowrun?)
Heroes - historical adventure
Ironhedge - fantasy-first genericized quick-play adventure in a variety of settings
Villains & Vigilantes - costumed heroes
Ysgarth - heroic fantasy, highly simulationist
Archaeron - magician-based heroic fantasy snippet?
Basic Role Playing - a lite, genericized version of RuneQuest
Beasts, Men & Gods - heroic fantasy
The Castle Perilous - story-first heroic fantasy
Dallas - do I have to include this?
DragonQuest - heroic fantasy which puts the Dragon Quest 1 map music in yr head
The Fantasy Trip - heroic fantasy by Steve Jackson
Land of the Rising Sun - historical adventure in Japan; somewhat mystical?
Melanda: Land of Mystery - heroic fantasy with unusual magic system
The Morrow Project - post-apocalyptic science fiction with cryonically-preserved armies
Odysseus - historical adventure in classical Greece
Skull & Crossbones - historical pirating
Space Opera - correctly named
Supergame - costumed heroes
Thieves' Guild - heroic fantasy for skulking about
Top Secret - spy-film system