I've always found it sort of strange that, since 3e (with it's grid-based combat), there hasn't, as far as I know, been a D&D-based computer game that actually uses a grid and turn-based combat system. I know that's not exactly the most popular genre these days, but it still seems like an obvious choice. All the D&D games seem to translate it into a (pseudo) real-time combat system. Temple of Elemental Evil came closest, and I loved that engine (despite the game being pretty buggy). Wish someone would do something like it.