I suspect the biggest problem Hannibal Rising had with critics and the public is that they almost entirely reviewed one of the two experiences to be had watching it. In fairness, it is the one they were promised.
As a prequel to the movie series Silence of the Lambs, Hannibal and Red Dragon (or at least an adaptation of the novel/co-developed project with the novel Hannibal Rising by Thomas Harris, which is a prequel to his novels Red Dragon, Silence of the Lambs and Hannibal). Now that I've retread that ground well enough, let me agree with previous viewers that by that criteria, it's pretty lousy. I didn't want an "origin of Hannibal Lecter" story, quite frankly, and this isn't a very good one, at that.
On a whole other level, however, as a kind of anti-Doc Savage in a Count of Monte Cristo style adventure/revenge story, well, it's damn good. In fact, it may sit next to Manhunter as my favorite movie to feature the Hannibal Lecter character.
Yes, some of the smaller touches, the proto-Will Graham/Clarice Starling relationship he has with Inspector Popil, oddly played by Dominic West, is interesting and occasionally entertaining, if underdeveloped, from the prequel perspective. The larger implications are mostly silly, however. Frankly, I'm not a big fan of the series of stories. It never captured my imagination the way it did other people.
Frankly, both the books and the post-Manhunter movies focus too much energy away from the broad stroke/pulp storytelling aspects of the stories, and I think those are the strongest element. Partly, I suppose, because of my affinity for pulp, but mostly just because I think that the dramatic arcs of them aren't nearly as good as their reputations suggest, which is a whole other discussion frankly.
I think those who come to Hannibal Rising looking for a fun little revenge thrilling rather than a complex drama or compelling character study will find plenty to enjoy, however.