so... 9 races x 2 genders = 18 voice actors for the races, with seannanners bean, and pats stewie. that makes 20 voice actors for Oblivion. and I have absolutely no clue if there were more in Fallout 3 although it felt much less apparent than Oblivion, but the voices were obviously very recycled nonetheless. But Todd Howard said in a podcast that the devs recognized that they needed more voice actors, due to criticism on the matter, and they hired a lot more voice talent this time. I think it was 40+ voice actors but I can't be sure, I'll have to look back on the GI coverage and dig up what I can.
10 Voice Actors for the races.
Craig Sechler = Male Altmer/Bosmer/Dunmer
Michael Mack = Male Redguards
Linda Canyon = Female Altmer/Bosmer/Dunmer
Wes Johnson = Male Imperials
Gayle Jessup = Female Redguards
Catherine Flye = Female Bretons/Imperials
Ralph Cosham = Male Bretons
Lynda Carter = Female Orcs/Nords
Jonathan Bryce = Male Argonians/Khajiits/Orcs/Nords
Elisabeth Noone = Female Argonians/Khajiits
+ 3 Celebrities
Patrick Stewart = Emperor Uriel Septim VII
Sean Bean = Martin Septim
Terence Stamp = Mankar Camoran
= 13 total actors for Oblivion