Okay, so I will start off by saying this...a LOT of people were disappointed in the cast. Especially with Kristen Stewart playing as Bella Swan. I was among those saying this. I mean seriously...the girls has no expressions. She was just a dull girl thru out the entire movie. Those parts where she should have had the most expression on her face just left us all half full at best. Sure they had some chemistry. I have watched several movies and I think the best actress who could have played Bella would have been Emma Watson. I mean she is a great choice for a lot of rolls. But after playing Hermione in Harry Potter...she could have nailed being Bella. Would have been right up her alley. Plus, she is pretty and had more expressions than Kristen.
Emma Watson as Isabella Swan
I was also very very disappointed in their choice for Edward Cullens. Okay...Robert Patterson may have been okay for Harry Potter as Cedric Diggory...but once that character was killed off that should have been the end of him. He wasn't that great. And he certainly does NOT scream smexy vampire to me. Hard to think of vampire beibng smexy when sparkly but still. Use someone who can be smexy anytime...like say...Kevin Schmidt. Now that one is super smexy and is a really good fit for the role as Edwards Cullen.
Kevin Schmidt as Edward Cullen
There is only one other role I wasn't the biggest fan of and that was the role of Rosalie Hale played by Nikki Reed. Nikki did a good job but...I just wasn't feeling it. Who I think could really pull off an even more amazing Rosalie comes down to two people. They are sisters and I think either of them could really have it down.
Aly/AJ Michalka as Rosalie Hale
Now the rest of the cast was pretty much spot on. I especially would not change the cast who did Alice, Jasper, Carlisle, Jacob, and Emmett. They all did amazing jobs. As thou with most movies based of books...the movies did not do enough justice for the books.
I were to recast any movie this would be it...and just those three character. They just weren't enough to fit the roles they played, while other did there roles very very well. It may not have been as exciting to read this but this was my attempt.