Dark Knight was awesome, and true to Batman's character. it seems like so many people want to make all comic book movies like that now. We don't have to copy the Dark Knight.
For one thing Batman has been referred to as the Dark Knight for a long time. Spider-Man is not Batman. His movies don't need to be dark. Just because it worked for Batman, that doesn't mean we need to copy it for every superhero movie.
Spider-Man titles were never called Spider-Man Legends of the Dark Spider.
He's not a dark character. For one thing with the mask on, he's suppsoed to be kind of a cheerful, wisecracking, happy go lucky hero with smart ass remarks.
They made a dark spider-man movie already once. It sucked.