I think you guys are spoiled, to be honest.
I remember when you paid $60 for a video game that gave you 20 hours of gameplay, now everyone and their mother wants to play F2P MMO's for "unlimited" gameplay? It's a farce, and a scam. You still end up paying monthly or there is a system implemented where the game isn't fun unless you pay somehow for it.
You end up paying more and more, for example, monthly charges, "Rubies" or other sources of gems or currency to support MMO's that still only give you limited gameplay.
Diablo 3 has been out for 4 days. The people beating it in 4 days are rushing, skipping content and dialogue, skipping everything they can and there are still 60-70 hours of quality gameplay here to be had.
Plus, unlike mmo's and other games, the content is truly randomized and as you get to harder difficulties traps and new areas you haven't seen before start to appear. 70% of the items (visible) can't even be found in normal mode alone.
I still think most of these complaints are originating from baseless nooby experiences, BECAUSE the game is designed for 60+. Getting to level 60 and hell mode is the beginning of it - and by that I mean you don't really get to customize *everything* until 60. And even then there are tons of armor sets, rare, and legendary items that are randomized well into inferno mode that you can customize even further with unique armor dyes and the like.
There's just so much more depth to the game than the face of it which is where most of the complaints seem be to stemming from, but if you don't care about hack and slash games like this then that's probably another good reason why, you're just denying yourself from saying it outright.
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And it takes about 20 hours to beat normal mode, I played from 4:15 AM at release for nearly 40 hours before I finally beat it because I was taking my time.
I'd go on to list multiple games you pay $40-60 for that only give you 20 or less hours of content that were huge hits but I'll save myself the trouble and not do that.
I'd also like to say there's tons of character depth and each character has their own story throughout Diablo 3. The followers also answer and talk to you about different things with different backgrounds as each hero class.