I actually own a copy of the core books for nearly every edition of D&D, except for 4th edition.  I've also been able to borrow some of the lake geneva pamphlets, though I haven't actually played a game from them.  (I still had the chance to read the original pamphlets, plus the greyhawk campaign booklet.  Seeing android in the monster section and laser pistol in the magic item section is a bit of a trip)  2nd edition is by far my least favorite, but it's cheap enough I still own a bit of it.<br/><br/>4th edition I refuse to get on the basis of 2 out of 3 sessions I ever play of it involving fighting a white dragon.  (and the simple fact that it doesn't support the sort of playstyle I enjoy, which is old school style structured adventure sites with contingiency plans, rather than per encounter design and pre planned scenes/set peices.  Even if exception based rules are indeed superior, it still feels like the new school parts of 3.5 welded to even more new school stuff, and the D&D I love just isn't there anymore)