This is not to mention that Diablo II is gargantuan in size (over 1.5 gigabytes hard disk space for a full install not including the expansion pack) and has gameplay stretching out over four different 'acts'. Each act takes place in a certain area (desert, forest, etc) and is comprised of several different seamlessly interconnecting 'levels' including the designated non-combat town area where you'll frequently return to unload your found items and to do business.
The storyline in Diablo II picks up from the original Diablo and begins by telling you that Diablo, Lord of Terror, is rumoured to be walking the earth again and that a dark wanderer has passed through the region recently leaving 'a trail of evil' in his wake. Shortly after the wanderer passed through, the countryside began to be overrun with 'strange creatures'. The story is then further developed through a series of quests which you must undertake and complete in each act of the game culminating in facing the act's boss monster whom must be defeated before proceeding on to the next act. The final act in the game has you confronting Diablo himself (and all the hellaciousness entailed therein).
The graphics in Diablo II won't win any awards but they certainly do the job and provide enough visual stimulation —especially when playing as the Sorceress— to make the game a hell of a lot of fun. As a video game classic, you probably won't be inspired to compare or even care whether Diablo II graphics were up-to-snuff in the year of its release. Some say they weren't although this probably has more to do with the fact that you could originally only play Diablo II in 640 x 480 screen resolution which was reportedly to keep everything fair in multiplayer mode. (The Lord of Destruction expansion pack changed this by offering the option to play in 800 x 600 resolution.)
I personally, however, was quite astounded by the graphical improvements in Diablo II, having played the original Diablo quite extensively. I found the artwork to be much more colorful and realistic was particularly struck by the detailed outdoor environments, the weather effects and the day/night cycle. For indoor scenes, e.g., the 'dungeons', the lighting is much improved. Diablo II does not have that washed out look of Diablo I making it a lot easier to simply see stuff (which is paramount in a game that focusses on collecting items). I also loved how certain gory details —such as bloodied scenes of medieval torture devices— are peppered about the gamescape subtly reminding you that you are indeed in a very dangerous place.
In some cases, the mere presence of graphics in Diablo II was a huge improvement in and of itself, e.g., the NPC vendors' screens present graphical representations of all the items they have for sale instead of just showing a text-based menu as in Diablo I.
All in all, Diablo II graphics are far from being an insult to today's standards and this is definitely not one of those classic video games where you'll take one look, turn up your nose and say "Egads... I can't believe I used to play pixelated crap like this." This game is still a joy to restart even after playing contemporary photorealistic heavyweights like Crysis and Far Cry 2.
Soundwise... Okay first of all, I have to admit that I am probably the pickiest video game music critic on the face of the planet as in, with the exception of a few shining stars, it all sounds the same to me. (And there is only so much cheap repetitive second-rate midway carnival music I can take.) Typically, within the first five minutes of starting a new video game, I'm rushing in a panic to the game menu to see if the developers had the sense to provide an option to kill the music. And truth be told, there are a number of games that I payed good money for but never played past level one because there was no such option.
Then came Diablo II which was in fact the very first video game I have ever played where I never felt compelled to turn off the music. Never. In fact, I tried it once and then two minutes later found myself rushing in a panic to the game menu to turn the music back on again. By way of comparison, I think the music in Command & Conquer: Red Alert is fantastic but eventually I turned it off.
The soft lilting music in Diablo II, however, with its Eastern influences and classical overtones perfectly sets the mood for a landscape that stirs one to utter 'beware of foul demons and beasts' upon entering and, for some reason, never seems to get repetitive or tiring. In fact, the game feels distinctly empty without the music.
The game's sound effects go along perfectly with the subtly sinister atmosphere set up by the music and range from high pitched death wails of the so-called Dark Hunters to the moans and groans of the Hungry Dead (read: zombies) to the grating childlike voices of pint-sized demons crying out to their god Rakanishu (the latter of which I'll also never tire of and find positively hilarious). I'll also never, ever tire of that lovely ching-ching sound of gold piling up whenever something is sold on one of the NPC vendor screens.