I had already in other posts voiced my complaint against voice-acting, without delving much into the reasons. I shall do so now, so that my whimpering grumbles are given some frame of reference. Also, it could prove beneficial to analyse how the voice-acting trend has evolved, what implications it carries, and whether it is a sensible thing or not to reclaim previous methods of narrative construction.
Before the objecting can begin, I have to make a disclaimer: I don't think all voice-acting is detrimental and ought to be removed so we all read huge chunks of tasty prose. As with pretty much everything in life, a balance has to be struck. Such balance would comprise all the benefits of characterisation by voice-acting without overwhelming game design or overshadowing player identification.
A character's voice is extremely definitory, not only for its particular texture, but also for the nuances with which the lines are read. Sometimes, a character's voice proves to be more powerful than any other traits he has been bestowed. It was the case of Garrus, whose voice made him the focus of attention of thousands of romance-inclined players; or Tali's, which I found particularly annoying due to its high-pitch and grating echo. It's a matter of taste, but decidedly significant in a character's appeal and general depiction.
Sometimes, voice-acting sets a particular tone for the story, not only the character. One of the things I enjoy the most of my adventure games is the construction of the main characters through their voices. I am particularly fond of the characters in The Book of Unwritten Tales, an adventure game which mocks the conventions of the genre and satirizes other games (with a pink-clad paladin who uses bubble-hearth. Loved it). In TBOUT, the skimpy elf is given a very British accent to depict her posh high-forest-class attitude. In adventure games there is no need for choice and consequence (at least, it was not the core element of both old and contemporary adventures), and the focus is placed on one immovable narrative that has to be peeled off from the coat of game mechanics: investigation, puzzles, exploration, etc. There is little room for hermeneutics. Identification with the protagonist is accessory, as she will be your vehicle into the narrative, not the tabula rasa into which you will project yourself. Even characters such as The Nameless One (Planescape: Torment), with such a pervasive background story, are subject to your roleplaying, your acting.
Indeed, the keyword is acting. We have to bear in mind that voice-acting is a manner of acting. In its absence, it is our ego the one which fills the void-text. When there is an alien -meaning "different from ours"- voice, the illusion of roleplaying perils. Moreover, if the text is voice-less, it will carry by nature more potentiality than the voiced one. Thus, any script for a play, unless provided with annotations, will be read differently depending on the interpretation of the actor. What we usually find to compensate for this formlessness of the dialogues in games are the descriptions of a character's voice, gestures or attitude. On many occasions we are not given such descriptions, especially when the line belongs to the PC; therefore, we imbue it with whichever tone we see fit. When there is a text describing the action that accompanies the lines, sometimes it is a gesture that could be rendered, more or less effectively, through animation and graphics. For instance, the Blackwell games, which actually have a top-notch voice-acting, had a hand-drawn portrait of the main character, Rosangela, smiling awkward and frighteningly; brilliant characterization.
But sometimes the written word is necessary. This same argument is valid for movies, especially for book adaptations. Nonetheless, the video game media allows for a much more seamless interaction between the written word and the audiovisual, and thus I consider that the argument is much more productive. We are not discussing which one is better, books or films, but rather how we can integrate into a neutral medium the best characteristics of both.
Literary descriptions allow for a more complex and subtle depiction of moods, gestures and environment, especially through the use of metaphors and comparisons. Depending on the description, an adaptation to the graphical interface can or cannot be made. For instance, you could easily translate a "She smiled" sentence into a gesture. Even a "She smiled wryly". But how can you convey "She smiled as if she had been trained for it, as a soldier has been trained to smother hers"? The metaphor serves the double purpose of detailing the image with more -imaginative- precision, and of attaching to it a certain undertone. In this case, stating that it is a mechanical smile, and associating it to a militaristic dehumanization. A translation into the visual could perhaps make explicit the unnatural quality of such a smile, but never the association that the comparison suggests. How can you translate an uneasiness, a longing for home, as in Eliot's "when the human engine waits / Like a taxi throbbing waiting"?
The old RPGs drew from the literary source much more than current games. The writing quality, in general, was better. I have argued how they benefited -and can continue to benefit from- the written medium. The nuances of literary expression in addition to a graphical interface with sound and music. The integration of all of these engender games such as Baldur's Gate or Planescape: Torment. Too much focus on the audiovisual, and we obtain Mass Effect, where the writing quality is poorer and there is much more reliance on the visual, sensationalistic aspects of games-as-movies.
Back to the topic of voice-acting, I believe that providing the protagonist with a voice is a bad idea in the context of RPGs. Along with many other things that Bioware did wrong, its voice-acting, although superb for FemShepard, had the fixation of reminding me that this was not my story. Coupled with the dissonance between the answer you seleced and what the character said, ME and DA2 felt more like an interactive movie than an RPG. And in the end I was proved right, because the choices, the core element that they were brandishing as the peak of roleplaying, were inconsequential. The choices provided a flavour. How do you prefer your Shepard, angry or sanctimonious? If Bioware wanted to tell me their story, why didn't they make an adventure game, for instance?
Yet another problem with voice-acting is the cost, and what it implies. Unless your budget is infinite, you'll prefer re-using some parts to recording entire scenes for different inputs. This doesn't happen to the same extent with written text. Although writing is a laborious endeavour, it is definitely less expensive and more flexible. I always cringe at the announcement of a fully-voiced RPG, because I know that there will be significant cuts made to dialogue in order to reduce costs for what I personally consider unnecessary: to have everybody in the game speak with their own voice, minor and major characters alike. I am thrilled to hear a major character speak, standing out from the crowd of voiceless characters. I don't think that hearing Space Janitor #3 is a particularly fascinating experience.