Eh, since others are chiming in...
D&D Holmes - 3 (one in the box, one reproduction - book only, one lost)
D&D B/X - 2 (still have one, in the box)
D&D BECMI - 1 (still in the box)
D&D Rules Cyclopedia - 1
1E - 1 (+ UE, still in one piece)
2E - 6 (still have 2, one original, one revised; one given away as a prize at a con, signed by Larry Elmore)
3E - 5 (still have all, two 3.0, two 3.5, one 3.5 deluxe)
4E - 1 (& PHB2, PHB3)
5E - 3 (still have all 3, one is falling apart, one regular, one foil-covered)