Randomly mapped levels, quests with rewards that are actually worth it, constantly challenging -- hack and slash had never been so great. At the time this game was released, this was a breath of fresh air. Blizzard knows what people want and how they can deliver it.
The story is what you would expect with openings to hell (the game IS called Diablo) and magic galore. Playing throught the game is linear, but playing through once will not give you all of the quests.
The levels are randomly created. Why is this nice?
1.It increases the replay value.
2.You have to figure out the game yourself.
Blizzard (thankfully) gave us a map to use. So, even though your not really sure what you'll find around the next corner, at least you will be able to find your way out.
The inventory gives you just enough slots to make you wish you had more, but not enough to let you hang onto everything. I thought one very unique factor with the inventory system is that gold actually takes up a slot. 1 slot can only have 5000 gold max.
There are enough spells to make magic use enjoyable. Pleanty of armor, weapons, and items make you really decide how you want to advance your character.
Obviously, it can't compare to games like Dungeon Siege of today. It's apples to oranges; different time period, much different computer capabilities.
Summary: If your looking for a pure hack 'n' slash that won't tax your computer, look for this bargain bin classic. Put it on your "Must Play Once" list so that you can at the very least experience some great flavor of the past.