List of LucasArts games on Wikipedia, pre-2005, released on DOS or Windows, excluding stuff that's already on Steam (although they could certainly re-release, it'd obviously be less significant that original releases), bold for notable stuff:
PHM Pegasus
Maniac Mansion
Strike Fleet
Battlehawks 1942
Zac McKracken
Indiana Jones and the Last Crusade: Platformer
Pipe Dream
Their Finest Hour
Masterblazer
Night Shift
Secret Weapons of the Luftwaffe
Indiana Jones and the Fates of Atlantis: Platformer
Day of the Tentacle
Sam and Max Hit the Road
Star Wars: Chess
Star Wars: Rebel Assault
Star Wars: X-Wing
Star Wars: TIE Fighter
Full Throttle * Updated remake coming from DoubleFine.
Star Wars: Rebel Assault II
Afterlife
Indiana Jones and His Desktop Adventures
Mortimer and the Riddles of Medallion
Star Wars: Shadows of the Empire
Curse of Monkey Island
Outlaws
Star Wars: X-Wing vs TIE Fighter
Star Wars: Yoda Stories
Grim Fandango * Updated remake from DoubleFine.
Star Wars: Behind the Magic
Star Wars: Rebellion
Star Wars: Rogue Squadron
Indiana Jones and the Infernal Machine
Star Wars Episode I: The Phantom Menace
Star Wars Episode I: Racer
Star Wars: X-Wing Alliance
Escape from Monkey Island
Star Wars Episode I: Battle for Naboo
Star Wars: Force Commander
Star Wars: Galactic Battlegrounds
Indiana Jones and the Emperor's Tomb
Secret Weapons over Normandy
Star Wars: Battlefront