Prophecy

Diablo isn't a Real RPG. Its close but not exactly there. If you want a great RPG look at the computer and the PC only RPGs. All the major console RPGs have been on PC and not the other way around. All the Final Fantasy games can be found on PC in some form or another.

First is Bioware. They are the current kings of the pc RPGs and dugeon crawlers. Baldur's Gate, Baldur's Gate II: Shadows of Amn(BG has 2 expansions Tales of the Sword Coast and Throne of Bhaal) are wonderful RPGs.

Black Isle Studios developed Planescape:Torment that is also an amazing RPG. The have also released Icewind Dale and Icewind II, two of the best dugeon crawlers on the PC.

Then you have the Fallout games by Interplay.

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La Disciplina È La Mia Spada,
La Fede È Il Mio Schermo,
Non salti Ciecamente In Incertezza,
E Potete Raccogliere Le Ricompense.