I started playing Basic D&D back in '81, but that quickly morphed into playing AD&D as it was a much richer game system. My group quickly switched to 2nd edition when it came out years later, missed the demons & devils, but they were simple enough to put back in.
I'm not really sure why a person would play 1st edition AD&D, except for nostalgia's sake maybe. The rules are a chaotic mess, and not just for the number of books needed. Take the
DMG, for example... One of the most disorganized rule books I've ever seen, and I've seen plenty... 2nd edition rules are basically the same, just much more cohesive.
2nd edition AD&D also fixed some glaring problems with the original rules. Weighing items in "gold pieces"...? 2nd ed. sensibly uses pounds. Remember Deities & Demi-Gods, which encouraged player character god-hunting expeditions? 2nd edition cleaned that up nicely in Legends & Lore with the concept of avatars. Wimpy dragons? Characters thought twice before taking on 2nd ed. dragons. Your character had no abilities beyond what was listed in the character class? 2nd ed. added a badly-needed skill system -Which the lack thereof was always D&D/AD&D's Original Sin...
I haven't played
d20 D&D yet, but I'll give it a shot at a convention some time. The concept of Feats is interesting, and I like the increased emphasis on skills. What I find odd is attempting to use the
d20 rules in modern/"realistic" backgrounds to which the heroics-based rules hardly seem suited. Oh, well...