A lot of people consider Death Note to be a terrible film especially if they are avid fans of the series. In the beginning, a lot of people were excited about it mainly because they feel that it is going to be completely different from what they expected.
A lot of people are disappointed that it does not seem to be artistic at all. The fact that the lead is an American and the area where the series supposedly took place was changed are already some facts that fans cannot overlook. There are so many changes with the culture that the characters followed. These are just some of the reasons why people think that this is a bad film.
The reason that many fans of the manga and anime Death Note do not like the film adaption of Death Note is because the characters simply did not translate as well as in the other forms. Everyone who loved Death Note watched the movie and compared characters from the movie to the character in the manga/anime and it just was not the same.
This is often the case for people who are hardcore fans of a book and then the movie does not live up to the expectations. You have to watch the movie with an open mind and try not to compare them to each other in order to really be able to judge whether it is a good or bad movie.