I, Frankenstein is sort of a fantasy extension of what happens after the classic Frankenstein story. In short, he joins the war between demons and gargoyles, and saves humanity. Mostly it is just a generic CG battle story between two races.
The movie does not make any effort to let the audience care about any of the characters. For a long time, it is unclear why we need to have Frankenstein in such a generic war. When we reaches the final part of the movie, a reason is revealed, but just when the story starts to get slightly more interesting, people do unreasonable things to move the plot forward. The relationship between Frankenstein and human ought to be explored far deeper than the superficial treatment we are given here. There are other problems with the movie, e.g. with the appearance of the characters, but these are minor compared to the aforementioned critical flaws. This movie reminds me of Blade (1998) – although I didn’t consider it to be really good, at least it is significantly better than this one.