Exile 2 FTW.
Other engine changes I can remember between E2 and E3: expanded (and improved) PC advantages and disadvantages, more inventory slots (24 instead of 16), encumbrance exists, acid exists, a few spell changes.
The nice thing about Exile 3, that overcomes the surface setting (about which I agree with Alorael), was its vibrant color. It both looked fun, and was fun to play. Avernum 3 lacked that entirely.