On my "active gaming" shelves: Original D&D + Supplements, 1e AD&D
On my "reference" shelves: Holmes, '81 B/X, '83 BECMI and RC
In storage boxes: 2e AD&D, 3.0 D&D, Castles & Crusades
Never bought 3.5, 4e, or Pathfinder (and have never played Pathfinder).
Oh, I also have copies of OSRIC, Swords...