Nathan Fillion. Now this might seem strange, as many people (including myself) would also like to see him as Nathan Drake from Encharted. But I recently saw White Noise 2, and Nathan can also pull off the eerie, serious type. And I think they sound alike, and maybe with some facial hair, they even look alike.
I say just use the actor they rendered him off of and used in the music video by Poets of the Fall and the Bright Falls mini series, Ilkka Villi. They use Ikka for the appearance then have Matthew Porretta (Wake's voice actor) dub over Villi's performance.
To me, Nathan Fillion is already associated with one writer and that is Richard Castle. Plus, he's put on a little bit of weight since his Firefly days and doesn't quite feel right, to me anyway, for Wake.
I do agree with Android... Matthew Porretta would be a great choice as it is his voice in the game. Plus, while he doesn't necessarily look as close to Alan Wake as other choices, it's close enough and he has decent Hollywood experience. It would also be nice to see him get a big break.
If you were going just by looks, someone's suggestion of Patrick Dempsey is pretty good. I'd also throw Dylan McDermot's name into the ring as he definitely could pull it off. And, I have never seen Ilkka act (or even hear him speak), so I can't judge. Plus, most studios are so conservative and that is a *huge* gamble unless he had major support from Microsoft or something.
I'd love to see them make an Alan Wake movie. Getting the right writers in for the job, I think it can have great potential! For the role, I am picturing John Cusack. Sadly though, I think it would be to close up to the character he played in "1408".