Im guessing graphics are not an issue, but all the games i can suggest have fairly decent graphics and the best gameplay.
Temple of elemental evil - turn based D&D with the best sound track i have ever heard. (GoG)
Diablo games are all worthy of playing.
The Bards Tale - On steam, very funny game.
Icewind Dale 1 and 2 - Both on GoG for a few quid.
All the Spiderweb games such as Avadon, Avernum and Geneforge.
Neverwinter Nights
Dragon age 1
Divinity games (Divine, Beyond and 2) - First two available on GoG.
Arcanum (GoG)
Drakensang (1 is better than the second)
Planscape Torment (GoG)
Nox - A bit like Magicka/Diablo but less frustrating. GoG again.
Fallout 1 and 2 (GoG!)
The witcher games.
Dungeon siege 1 (Gets a bit repatitive)
Torchlight - hack and slash like Diablo.