Now it is, but before he was cast, it was more up in the air. Daniel Day-Lewis has the jaw for it.
I think Sean Bean would have been a fine Aragon.
Interesting about the sword-fighting in the old costume dramas. Bob Anderson, the sword trainer and choreographer, did absolutely everything from Captain Blood to Star Wars. He was practically the one-and-only in that business.
Sean Bean was a good Boromir, but is wiry enough for Aragorn. Mortgenson is an obsessive artist type. You should read how he got into the part. My favorite of all for perfect casting- Karl Urban as Eomer. Took a bit to get into him playing Bones on Star Trek (movie), but he did ok with the voice.
I think Daniel-Day Lewis would have made a very interesting Aragorn.