Tracey John, over at MTV got a chance to go over some fan re-creations from the Diablo III trailer with lead designer, Jay Wilson. These re-creations were all touched up via Photoshop and it's noted even by Jay that these are not done via the game engine and to keep that in mind as some things done cannot be actually reproduced in game (ie: lighting).

Jay points out quite a few flaws with the fan images. Some major points include mundane and repetitive textures and lighting which makes everything seem the same, loss of details by making things darker and also the quality loss by even darkening the spell effects, which, even isn't what Diablo II had going for it.

In one shot on a bridge you could see a rainbow, in the fan version the rainbow is totally gone. Jay comments on this making a statement that the designers probably did this on purpose.

quote

I think our artist just put [the rainbow] in there because they knew that’d be controversial. And I’m sure they were like, “Well we’ll see how far we can push it.”

While some of the fan versions do look pretty good in some aspects such as the texture and lighting on the architecture there's also quite a bit of other things that make it not so appealing. With the fan versions there are a lot of details that are missing.