I know what you mean about Ash... I had to watch one of the subbed episodes when I missed a new dubbed one during the N/Team Plasma/Reshiram conflict, and I was like, "Ugh... Satoshi... voice... ughhh..." And his speech pattern (aside from the whole "Japanese has a different syntax and cultural context" thing) was just... ugh.
But I loved the dub voices for Brock, Misty, May, Max, Dawn, and especially N... they made a really excellent choice in a voice actor for N.