In addition, there was a skill tree where experience levels let players allocate significant points to skills desired by the player. This process allowed customization that required an investment of time and enhanced meaningful player abilities that didn't rely solely on items as it does in Diablo 3. In addition, rune words and other modifiers in Diablo 2 motivated players to consider white (non-magic) drops because they could be utilized with correct rune words. The multiplayer cap at 8 instead of 4 enhanced the multiplayer experience which in turn accelerated players' motivation to add other players to their friends list. This motivation propagated players to play with groups they were familiar with, and this process alone reinforced players to continue to play the game.
Diablo 2 was excellent at keeping a player base and had an enormous replay value due to skill point allocations allowing variances which allowed for recreating even the same class with a different result. The game designers of Diablo 2 were intelligent in their design. I hope the developers of Diablo 3 are receiving our feedback, and are adjusting the game accordingly.