Why the thread necromancy ?WISE FWOM YOUAH GWAVE
AD&D Player's Option, hands down; like Unearthed Arcana, not all at once.
3.X is second place if and only if it's 3.PF, Gestalt, with liberal acceptance of first-party supplements.
Third place is Rules Cyclopedia with any tolerable form of multiclassing house rules.
Why the thread necromancy ?
Ironically the more I hear about Pathfinder 2E the more it makes me appreciate D&D 3E!