The first Diablo was my 3rd RPG, after AD&D Treasure of Tarmin on Intellivision and Castle of the Winds on Windows 3.1. I liked it, but once played it twice I wasn't interested anymore, when Diablo 2 was released I didn't buy it, but later I bought a budget edition of Throne of Darkness, that IIRC used the same engine. Initially I hated it, but after getting used to some controls I didn't like, I appreciated it very much.
I won't buy Diablo 3, anyway.