Now, I'm wondering, taking into consideration the fact that by the time Alec Guinness did the original Star Wars he was already something of an icon unto himself, a well respected actor of high regard and a very impressive career with many memorable performances before Obi-Wan Kenobi.
With that in mind, I wonder if the more appropriate ghost of Anakin Skywalker would have been altered if he had been played by an actor who's name bore star recognition similar to that of Alec Guinness. Imagine, for a moment, if the old-man-turned-ghost of Anakin had been played by someone like Burt Lancaster or Charlton Heston (and yes, Heston IS an icon of the old Hollywood machine, whether you like him or not); would George Lucas have dared to replace the ghost of Anakin Skywalker then?