Personally, I think the Playstaion version of Diablo is better than the PC version. For all of its faults, Diablo is best played in a multiplayer environment and the Playstation is an ideal platform for this.
The graphics are just as good as the PC and the sound and control are good.
The mission is to destroy Diablo, a demon, and his minions who are terrorizing a small village. This is a fairly basic plot and you won't find anything surprising in the story. The game is quite gory and will satisfy your appetite for destruction. Also, much replay value is to be had since the dungeons are spawned anew each time you create a new game.
Again, the game is alot of fun with a group of your friends and you'll quickly end up fighting with them, shouting and casting each other the evil eye as they fumble or cheering each other on as you help each other. But, playing the game alone is fun for a short while, but can quickly get repetitive.