He's not that big of an actor - he should be higher because he's the star but IMDB tends to list people by their credits and rating not just their importance to a particular cast. It'll probably switched around when the movie actually released.
Daredevil, Steel and Ghost Rider starred Ben Affleck, Shaq and Nick Cage; three lifelong comic fans who would've been familiar with the characters they were portraying. Spider-Man 3 was the exact same team as the first two. Catwoman came about because there 11 (ELEVEN!) different script passes...
They all do or at least claim to; you can't be too attached to one version of a character if you have to act anyway - you have to make it your own. Besides no amount of research is going to help if the performance is bad.
I'm thinking about getting my brother and sister each a new iPod Touch when they come out. Really, I'm much excited for Gift Wrap Wonderland at The Container Store
Lewis did his research and this is how he found Lincoln's voice described. Most of the people we think of as commanding and imposing didn't have those sorts of voices.