How important is voice-over work in a game? Since the dawn of video gaming, we have endured the 'text-speak', npc's that you couldn't hear, but you would have to read streams and streams of dialogue. Any Final Fantasy gamer is used to it, and lets face it... THIS was one of the 'Positive' aspects of gaming that you can espouse to people "Games aren't junk, they help in reading skills." True though that may be... slowly the gaming landscape is changing ... especially in the MMO genre. Next year Star Wars the Old Republic is promising full voice-over work, on EVERY single piece of dialogue. All professionally done. But it's not the only one, though I think it will raise the bar in immersion, and believability of the game. DC Universe Online also promises to use the actors from the JLA cartoon series, and add voice to the hero's. I think that once we hear and experience these games, it will be hard to go back.
But don't worry, MMO's will continue to produce material that we have to read, but it's like the difference between regular television, and HD-TV. Yea, you can always go and play World of Warcraft, or Final Fantasy, or Lord of the Rings Online. ... that's cool. But if the new games coming out Play really well, look amazing, and give the feeling of immersion, it will be hard to go back.