I'll disagree on all those (and the Ultima's etc in the grandparent comment). They were all focused on RPG and story first, then adding some action on top of th

I'll disagree on all those (and the Ultima's etc in the grandparent comment). They were all focused on RPG and story first, then adding some action on top of that (via isometric, fps etc. modes). Diablo changed things in that it focused on action first, whereas the RPG element is just an add-on. Its gameplay cycles between essentially going deeper in a dungeon that's becoming more difficult, obtaining/selling etc. of items/potions in town so that you can descend further. Its story isn't really of (heavy) importance.