Shortly after the screenshots of Diablo III hit the internet the inevitable complaints started. Many were upset about the lack of the light radius present in the other two games (although primarily in the original as it was a true ‘dungeon crawler’ in some respects while a vast majority of the sequel was outdoors) and the blue tinge to most everything. A petition was signed by around 50,000 fans and to their chagrin has been rejected by Blizzard. It seems that everyone working on the game likes the art style.
According to the developers they’ve gone this route for several reasons. First of all a level of ‘realism’ has been attempted by many games in the past years and some developers are beginning to avoid it, a perfect example being Team Fortress 2 which opts for a more deliberately cartoonish style. They wanted to make the game stand out from the all-bleak-grey titles like Gears of War. They have also said that since many of the monsters are dark in color themselves hordes of grey baddies running around grey backgrounds would make gameplay a little too stressful. They did say that the light radius effect might be popped in one or two places that it’s suitable though.
Source: Digital battle