Most of the user base here probably knows well at least the last two elder scrolls games, Morrowind and Oblivion. The latter was fully voiced, while the former only had generic greetings the NPCs performed while not engaged in conversation with the player. It may not be common knowledge, but it is a fact that the dialogues in oblivion were overall shorter than those of Morrowind and the number of topics the player could discuss was smaller. (http://www.uesp.net/wiki/Morrowind:Morrowind_for_Oblivion_Players)
Furthermore, while players can instinctively skim through long topics and only take notice of what interests them when the dialogues aren't voiced, with voice-overs the conversation will proceed whether the player cares for it or not, appreciates the voice-over job itself or not, etc... it can be interrupted, but that's obviously not the same degree of personal experience one can obtain with plain text.
The most important point to me is however the immersion factor. In Morrowind the game "froze" when speaking with NPCs, thus becoming a text game for the duration of the conversation, forcing the players to imagine the tone of the conversation to some extent while being stimulated by the occasional voiced greetings i mentioned earlier. The resulting effect was to me much, much more immersive than the voiced dialogues in Oblivion. Coupled with the overall increased text length and the ingame literature, i can easily say Morrowind had enough depth to it to swallow three Oblivions.
I would like to know what others think about the subject.