I played D1 as a child, and would probably enjoy D3 at that age. But I played D2 as a competitive older teen, and still come back to it.
Playing with the top 10% of gear is important to me in a game where the only success is defined in your gear. You killed Diablo? Neat, I guess. Bale? Ok, whatever. You have a perfect crown of ages? CAN I SEE IT?!
How much time have you spent oogling or being oogled on D2? Maybe I'm not in the majority, but I think I am.
The value in this system is the lack of constant new items. A Tyrael's Might from 10 years ago is still, today, awesome due to it's tremendous rarity. Now introduce TF2 buy your hats here system and the second you buy Tyrael's Might to be competitive they introduce Tyraels Superbigshoulderedheydoyouplaywowcuzyoushouldarmor.