This game is the prime example of how WRPGs should be.
Graphicswise, the game seems a tad bit outdated, even by PSOne standards. While you got various monsters and PCs on screen at one time, the game's surroundings are very atmopspheric, given the theme of darkness and evil that the game is built around. Also of great note is the CGI-rendered cutscenes that play when you reach a new Act out of a possible four the game has to offer.
In the sound department, the game has a very nice and eerie ambiance to it. The sound effects and the chatter of monsters in the provide a very interesting experience, especially with the zombies mutttering "Brains" while looking for some living being to eat his or her brain. Another facet of the game's sounds is the music, which has a medieval feel to it.
Regarding controls, Diablo II is top notch on the PC. Instead of using a gamepad or joystick, as in most games of it's nature, you use your mouse to move your PC, attack enemies, cast magic spells and use the occasional Healing potion, among other actions. Interestingly enough, the keyboard is used as well, acting as a quick hot-key command center. For example, to use a Mana potion that is on your PC's belt, you just press one of the four numeric keys, or in this case 1-4, that the item is assigned to.
As far as the gameplay is concerned, it's really fun and then some. While the main game has only 21 quests, most of them tied to the game's storyline, the game provides a ton of replay value in the form of unlockable difficulty levels. Also, what makes the game set apart from other computer RPGs is it's vast online muliplayer experience. On the closed Battle.net servers, you can have up to eight players in the same game going on quests and sharing the fun experieince with your or, if you're feeling very brave, try to attack and kill one of the PCs and loot his or her corpse. Even with the latest patches the online is extremely fun.
Overall, Diablo is the prime example of how WRPGs should be. No one should be able to miss out on this game.