Owes a huge debt to Se7en
Watched this last night for the first time and enjoyed it quite a bit. I thought the ending was a little weak, and they underutilized Embeth Davidtz and her character, but overall the film was well-made, had an interesting premise, and held my interest.
I couldn't help but notice, however, that the look and feel of the movie is very reminiscent of Se7en. Not only are they both, of course, serial killer movies, but the atmosphere, production design and color palette of Fallen absolutely evokes David Fincher's style and cinematography.
It seems clear to me that the studio executives were like, "Hey . . . so that movie Se7en is really popular . . . let's put something together that's a lot like it but we'll give it a little twist to make it different." And this is the film they came up with. Especially considering that this film was released only three years after Se7en, I'm sure the similarities aren't a coincidence.