If you like Diablo 2 and Hate Diablo 3, then buy Torchlight 2..
It has the same gameplay elements as Diablo games like character classes, skills, looting, crafting, alchemy, boss fights, pets and the like. The only weak part for me is the story. The story is minimal to non-existent in this game but the overall gameplay and experience is very satisfying. It also has multiplyer function via LAN and internet.
Other notable hack and slash RPGs ala Diablo are:
Revenant
Titan Quest
Titan Quest: Immortal Throne
Dungeon Siege
Dungeon Siege 2
You can also check out the Classics like:
Planescape Torment
Baldur's Gate
Baldur's Gate 2: Shadows of Amn
Icewind Dale
Icewind Dale 2
Fallout
Fallout 2
Games like Skyrim:
Morrowind
Oblivion
Fallout 3
Fallout 3: New Vegas
A mix of nice gameplay and great story telling:
Dragon Age
RPG Hybrids:
Mass Effect
Mass Effect 2
Mass Effect 3
Deus Ex: Human Revolution
So There..