12 years of hype, one decent game.
Diablo 3 is functional mechanically. Its a point and click adventure where you fight hordes of enemies and destroy them in the most gruesome possible way. Its not like an MMO as you don't fight enemies one at a time, or at most three at a time. No, in Diablo 3 its common to fight 15+ at a time and brutally slaughter all of them. Your character is overpowered and the fights are unbalanced... at first.
This is one of the problems with Diablo 3. Normal mode is ridiculously easy. I remember I killed Azmodan before he finished his speech threatening to kill me on my Wizard. Nightmare mode doesn't offer much more of a challenge. But Hell mode and Inferno mode are ridiculously hard. Unfortunately they aren't challenging hard, they are cheesy hard. For example, Champion mobs now have random enchantments. You can run up against a pack that can kill you in 2-3 hits with the enchantment "Horde-Invulnerable-Very Fast-Waller". What that means is there are extra minions that can 2-3 shot you, they're too fast to kite, only the leader is killable and they can create walls to box you in. This is a fight you can NEVER win. And this isn't the only set up that's impossible to overcome, there are LOTS.
In Diablo 2 this could be overcome with ridiculously overpowered mechanics, for example a Bonemancer (Necromancer specializing in Bone spells) could put the affected targets in a prison of bone with several tens of thousands of health points, and then kill them at his leisure. Melee classes had mechanics like whirlwind to remain invincible and enough life-leech to stay alive as long as they were swinging their weapons. Alas, this is not the design philosophy in D3. In fact, the developers have already blanket nerfed 3 classes (Wizard, Monk, Witch Hunter) that had mechanics that allowed them to survive these higher difficulties. It makes an experience where soloing is no longer possible and grouping takes several hours to do what you could do in the normal modes in 15 minutes. It remains to be seen if the highest levels of gear of Inferno mode purchasable on the Auction House will give players the edge they need to survive this punishing difficulty.
The graphics are nothing to write home about. They're fine, probably perfect as they're bad enough to let almost anyone play the game. The loot system is the same as D2 where you get whole arsenals worth of loot off of a single pack of mobs. The bosses are more challenging than D2.
The story is weak. D2 came out before Mass Effect, Dragon Age, Heavy Rain, Uncharted or any of these story-based games, and the D3 title doesn't really even rise up to be in the same league as these other titles which is unfortunate given its time in development.
All-in-all D3 is a fine game. It probably deserves a 7.5, but unlike most titles its under constant developer support and sees new changes reguarly and offers better online support than most titles will ever get. The always-online DRM sucks but DRM is here to stay whether we like it or not (and we don't). If you don't have a stable connection, sad day for you, but D3 the game is a fully functional, addictive, and fun dungeon crawler.