As a programmer (not a gaming programmer) I think the main reason why I would probably still be attracted to this game even if I wasnt already a fan of BG1 and BG2 is simply that in this project the programmers and artists clearly have been given the freedom and room to implement a game to its fullest potential.

Not many game programmers get this freedom and I think it shows in the product.

Also Larian managed to archieve this goal without going overboard, like a certain Star Citizen.