I have not read the book Eragon, so I didn’t know what to expect beyond the general storyline. I suspected the movie would be kind of a Lord of the Rings light, and a few scenes seem to be coming almost directly from the Lord of the Rings movies (for example, the scene where Durza is addressing his army is very reminiscent of the scene in The Lord of the Rings: The Two Towers where Saruman is addressing his army from the balcony of Orthanc); however, I did not expect Eragon to come anywhere near the Lord of the Rings trilogy, and I was correct in that assumption.
The cast is okay and does what is expected of it most of the time. Regarding Saphira, the computer-animated dragon—I kept alternating between accepting her connection with Eragon and thinking it was lacking in credibility, and I have to say that Saphira is a bit too human a dragon for my taste.
Eragon feels rushed, and the movie may have benefited from a longer running time. Perhaps a future extended edition will give us a more complete and better version, but judging by what I have seen, I doubt an extended edition can improve my opinion on the movie. It is difficult to do something with a movie whose characters and storyline are quite uninteresting and unengaging.
Eragon is passable entertainment, and the movie adds nothing new to the fantasy genre. Will I still see the sequels (there are two more books in the Inheritance series, Eldest and Brisingr), assuming they get made, at some point in time? Most likely, yes.