I occasionally play Diablo 3. Typically, I play it a bit, then get bored, and don't play it for six months.
I've come to realize that, when it comes to games, I mostly play them for the memories, and for the stories. This explains why I've never really managed to leave EvE (it makes memories like no other game), and why I found Sunless Sea to be, essentially, crack cocaine + heroin in game form for about three months (it's all about stories). I like building characters, but, eventually, I reach the Futility Horizon where I wonder why I'm looking for the next piece of loot instead of doing something enjoyable, like work.
Diablo 3 has one, short, not very interesting story, and very little opportunity for creating memories, even when playing with friends. To be honest, I just joined Aleksylva Paradox, and in the last two weeks or so, I think I've created more memories for myself (and enjoyable ones, to boot) then I have in one year of playing Diablo 3.
Make of that what you will.