Dungeon Hunter is your best bet to Diablo on the iPhone and it delivers.
The Bad: Gets boring after awhile, lame story, not enough variety
Diablo set the stage for hack & slash game play and looting for years to come, and Dungeon Hunter is probably your best, and closest bet, on the iPhone. With slick visuals and lots of items to loot the game is pretty responsive, and gives you a lot of powers and abilities to use so you always have something to pine for. There are a lot of creatures and locales in the game as well as decent boss fights, but the game does get repetitive after a few hours.
What surprised me the most was how deep this game was on a mobile device when Gameloft could have easily realeased the game with half the content. There are dozens upon dozens of weapons, armor, rings, helmets, boots, gloves you name it. Busting open barrels and treasure chests is rewarding and always makes you want to loot every corner. If your inventory fills up just transmute your items into gold. Of course you will get less than you would at a vendor, but it's better than just dropping items so this always you to keep what you really want.
Powers are upgrading when you level up, and you also get fairy abilities. Powers that fairies unleash and these are even more powerful than you spells. The story takes a back seat and isn't one bit interesting, but it's enough to keep you looting the game's many locales. The game looks excellent with lots of detail and very little slow down. So if you like Diablo style games then Dungeon Hunter is something you must have.