Time to market the Basic D&D options! (If I don't do your favorite justice, feel free to chime in.)
D&D Basic Set (Holmes, 1977): The original basic set, and the first attempt to consolidate and update the game. The missing link between OD&D and AD&D.
D&D Basic Set (Moldvay, 1981, B/X): The point where Basic and Advanced D&D really began to take their own paths, and the source for some of the most popular retroclones.
D&D Expert Set (Cook, 1981, B/X): (Re)introduces wilderness exploration to Basic D&D!
D&D Basic Rules (Mentzer, 1983, BECMI): The famous "red box", the main introduction to D&D for a generation.
D&D Expert Rules (Mentzer, 1983, BECMI): Mentzer's revision of the Expert Set.
D&D Companion Rules (BECMI): Introducing the "War Machine" rules!
D&D Master Rules (BECMI): High-level play for the Basic D&D rules.
D&D Immortals Rules (BECMI): Beyond high levels! Play at being gods, basically.
D&D Rules Cyclopedia (Basic D&D): The ultimate, definitive collection of the BECMI rules (minus the I).
B1: In Search of the Unknown (Basic D&D): The first ever introductory module for the game...
B2: The Keep on the Borderlands (Basic D&D): ... but this is the better-known of the two.
B4: The Lost City (Basic D&D): Notable enough to get remastered twice for 5e!
B7: Rahasia (Basic D&D): Before Ravenloft and Dragonlance, the Hickmans gave us this classic!
B10: Night's Dark Terror (Basic D&D): A bridge between the Basic and Expert rules.
CM1: Test of the Warlords (Basic D&D): Introducing players to the Companion Rules, to include empire-building!
X1: The Isle of Dread (Basic D&D): The introductory adventure for the Expert Set, an iconic sandbox that's been revisited in multiple editions.
X2: Castle Amber (Basic D&D): Another classic dungeon, infused with pulpy weirdness.
X4: Master of the Desert Nomads (Basic D&D): An underrated exploration adventure...
X5: Temple of Death (Basic D&D): ...and its sequel, forming an early adventure path!
X10: Red Arrow, Black Shield (Basic D&D): Following from the previous two, this triple threat uses the Expert, Companion, and Battlesystem rules.
Creature Catalogue (Basic D&D): Basic D&D's answer to the Monster Manual. (Or the Fiend Folio.)
Creature Crucible: Night Howlers (Basic D&D): Want to play werebeasts in Basic D&D? Here's how!
Creature Crucible: Tall Tales of the Wee Folk (Basic D&D): One of D&D's first dedicated treatments of the fey.
D&D Gazetteer: The Emirates of Ylaruam (Basic D&D): A fine supplement to the Desert Nomads adventures.
D&D Gazetteer: The Grand Duchy of Karameikos (Basic D&D): The first D&D gazetteer, and the first dedicated sourcebook for the Known World as a setting.
D&D Gazetteer: The Principalities of Glantri (Basic D&D): The Known World's magocracy.
Hollow World Campaign Set (Basic D&D): The pulpy inner world within Mystara! It even got a
video game.
Thunder Rift (Basic D&D): The final introductory setting for the Basic D&D game.
Wrath of the Immortals (Basic D&D): The Immortals rules, updated for the Rules Cyclopedia era.