I like Infinity Engine (it's because I know how to crack it open
). In my opinion, 2D isometric games as Baldur's Gate have much better graphics than 3D games as Neverwinter Nights.
The ultimate combination would be 2D terrain and 3D models (such as Lionheart, coming in August will have).
(I get worse headache after a night spent with a 3D game
.)