If you like Diablo well, Diablo III is certainly another one of those games, and easily one of the better ones. The systems within the game have been streamlined in very thoughtful ways, the gameplay is as compelling as it ever was (which will vary based on your tastes), and the game looks great. As a game, I highly recommend it.
As a complete package I’d still recommend it, but somewhat less. Here’s the thing: Diablo III is all about the co-op. And the co-op is very, very good. I was playing today, trying out the wizard, when my friend Irven dropped right into my game and started playing with me. Co-op is well put-together in a lot of ways: lots of great interface touches, easy trading, and individualized loot (meaning that, if you see it on your screen, it’s yours). So what’s the problem? The problem is that, even if you’re playing single player, you’re playing co-op.
What do I mean by that? If you’re playing by yourself, nobody else in sight, you still have to connect to the servers (which sometimes go down), you still have to log into Battle.net (though this is a minor annoyance), and you still have to deal with latency (though the latency isn’t bad most of the time). It’s most irritating when all you want to do is play single player but the servers are down for maintenance; when this is the case, you can’t play. Period. It’s frustrating.
Having experienced the co-op, I can understand why they designed it the way they did. The game is better in co-op, and everything about the game facilitates co-op in the best ways possible. If that’s not your thing though, be prepared to get annoyed from time to time. That said, the experience (again, if you like games like this) is worth putting up with some irritating qualities for.