I think you misread the thread title, this thread is about the worst voice acting, not best.
On a serious note, I believe Booooolooooo Saaaantooosi's accent was a legitimate Sri Lankan accent, and thus great voice acting. It still sounds hilarious, though. --- Baseless prediction as of 01/04/13 : the next Xbox will be called the Xbox On.
How have we gotten this far into the thread without mentioning Ultima IX? --- "In peace, vigilance. In war, victory. In death, sacrifice." ~ The Grey Wardens http://www.trueachievements.com/mygames.aspx?gamerid=71900