Being good in front of a camera is an entirely different skill to being good behind a mic as has been made clear by so many horrible celebrity voice overs in games. Take a look at this lollerskates http://www.youtube.com/watch?v=r6x7zWhsgQA and you'll see what I mean. The actress is Mena Suvari, she starred in American Beauty which won 5 Oscars. Good actress...tear-your-hair-out awful voice over artist.
Another prime example is Yvonne Strahovski (sp?) from Chuck, she's great as Sarah in the show, but is easily the worst VO artist in the entire ME series (She plays Miranda in ME2).
Less crappy "celebrity artists" and more quality VO artists plz. Jennifer Hale is great, and Simon Templeman is FANTASTIC (Zaeed Massani, ME2, and the Seneschal in DA: Awakenings). Now, I'm strictly butter-side-up, but even I swoon at Templeman's voice