But Aragorn was not supposed to fit your image of a kingly handsome prince! It is said in the book somewhere (maybe someone else can look it up) that between the two (Boromir and Aragorn) one would have presumed Boromir the royal one, he being more handsome, proud and strong. Aragorn's royalty was not so much in physical looks, as in wisdom, personality. Aragorn himself says (In chapter Strider) : "I believe my looks are against me." Bearing this in mind, Viggo was perfect for Aragorn.
And Sean Bean perfect for Boromir. I second that, Aredhel!