This game is old. It's slow, some enemies are frustrating because it's hard to catch up when they decide to run away, there are some other complaints here and there but all of the issues pale when you look at how wonderfully atmospheric the game is as a whole. I'm sure most of these other reviewers remember their first butcher appearance. Diablo 1 is a groundbreaking game experience and despite all of its faults it's 100% worth experiencing.
