Note: Although cyberfluxor cites "Boulder's" Gate as a Diablo clone, it's only the console games that are really Diablo clones.

The Baldur's Gate that came out on the PC is a straight-up RPG - the first in the Black Isle series...was released ~ 1998. From what I hear, the Icewind Dale games that were based on the same engine were a bit more action-oriented, but still not Diablo-style in true form. It's completely different from the other one for the consoles that had the three characters you could choose, and the bartender lady at that singing ghost tavern or whatever.

And I'm not exactly certain that Diablo really spawned this genre of games - but they certainly did do it best and most memorably (like just about everything that Blizzard does, to be honest). I mean, even an ancient game like the old Bard's Tale could be seen as a "dungeon hack."

Oh yeah - and the new Bard's Tale was actually released on both PC and consoles, so that would count as a "Diablo-clone."