My vote is for D2, D3 to me just wasn't a standout Diablo game at all. That being said, I was a massive D2 junkie all through highschool so my opinion is very biased here. D2 resurrected gives you a nice polished version of one of the most memorable rpg from that decade. The has aged incredibly well.
Have you checked out Path of Exile? It's a great, free game that you can go incredibly far with for free. I really love that game for it's graphics, gameplay, and character building mechanics.