This game is the perfect example of what's wrong with video games today. No plot, no roleplaying, and no imagination. Just grabbing the best weapons and armor possible and slogging through endless piles of monsters. Then, when Diablo's dead, you just start over.
But you all already know that I've spent endless hours playing this game. It's just so mindless that you have to keep going. To the next level, until you get a cool unique item, until you've beated it on a certain difficulty. Then you suddenly think, hey, what if I try THIS character? Will I like the game more? And it's back to starting over.
Truth be told, starting over's the best part of the game. The first act is so much better than the others that it's hard to realize that it's all the same game. When you're just starting out and everything's new and promising, everything looks right in the world. You gain levels quickly, you enjoy your new character's quirks, and you have fun while playing. But soon you're trapped in the web of looking-forward-to. And then the game stops caring about you having fun and starts worrying about making you log endless hours in front of the screen.
This game does, however, have some redeeming qualities. First of all the characters are pretty cool, if totally uncustomizable. The movies are neat, and the graphics are quite spiffy. The abilities are often fun to use, and it has a massively redeeming multiplayer.
However, this game totally lacks the kind of emotional attachment formed when playing its superiors, games that involve roleplaying, making personal decisions and characters with character.
Diablo II might have been better if the character portraits and appearances would have been customizable. That alone would have contributed hugely to the missing element of roleplaying. Also, adding some quests that involve thinking and character development instead of skull smashing would have made it more immersive. But it's still a good game to waste countless hours on. Just don't expect to feel any better at the end of the day.
One final note should be mentioned that makes this game quite fun: play it with friends. Lots of them. Any game can benefit from being played with lots of people, and Diablo 2 is no exception. Combining abilities and using team strategy adds a much-needed new element to Diablo 2, and almost (but not quite) solves the brainless click-fest fighting.