Jason Momoa?
Josh Holloway?
Holy fuck, dear casting director, do not listen to ERA for casting advice.
No americans please, PLEASE.
Nikolaj Coster-Waldau would actually work, although I wonder if he'd want to do that - it would pigeon-hole his casting type for the remainder of his career.
Although it would also be a great role, and I think he could bring a lot to it.
And whoever that was that said "but he sucks in sword-fighting scenes", please watch season 1 again, everything after that the dude is SUPPOSED to fight like crap - he lost his freaking fighting hand!
Curious to see who they cast either way, Mads Mikkelsen would definitely work as well, but I'd almost prefer to see a new / less known Scandinavian or Eastern European actor instead.
Tonnes of potential here, but as others have stated, I don't have the MOST faith in Netflix knocking this out of the park - although it 100% depends on who they actually hire to take on the task.
And guys, c'mon... we all know basing any of this series off of a videogame property would be a mistake.
Focus on the source material, ignore the world of videogames - they never translate successfully to film / television and likely never will [maybe I'm forgetting some exceptions or something? happen to be proven wrong, honestly].
Personally I'm more worried about the Amazon LOTR series - GRRM has advanced fantasy storytelling to the point I'm not interested in that kind of story anymore.
Witcher is already more interesting than LOTR and has far more potential to be intriguing in today's climate and with today's storytelling expectations.