Granted, if Wolverine in the X-Men sounded like an Australian, then you might have something to complain about. Or if Batman spoke with a Welsh accent, then that would also be something people could have a genuine gripe about. But the tonality of someones voice (unless its totally annoying like Pee Wee Herman or Bobcat Goldthwaite), should not enter into the debate if the acting is not a problem.
So, you agree: the way an actor voices his character can legitimately affect the audience's enjoyment of the film.
