"Viggo Mortenson played Aragorn in Lord of the Rings, etc."
Let's be honest. No one saw Lord of the Rings because Viggo Mortenson was in it. They could have gotten any reasonably good actor to play Aragorn and the movie would have been just has good and made just as much money.
Well, I did see Lord of the Rings. I do, however, defer to your insight regarding Viggo's part. You're probably right. He's not that deep.