Play fallout 3. Seriously beth improved on the voice acting ALOT. There are WAY more voice actors and dialogue options that are actually unique to the person your talking to instead of having the same conversation over and over again. They also put the topics in forms of actualy sentences and questions instead of just one word like "Rumours" plus they put in skill based dialogue.
F3 really gave me hope for the next TES.
Fallout 3 does give me a lot of hope for TES:V in a lot of aspects, and the more raw and real-sounding dialogue is one of those. But Fallout 3 has similar problems to make allowance for that dialogue overhaul. They have fewer NPCs, and a ton of NPCs that are non-interactive and just spout from a small pool of one-liners, like "Megaton settler."
Perhaps the solution, then, is to not spend exorbitant amounts of money on big-name voice-acting stars. Patrick Stewart, Sean Bean, and Terrance Stamp were all well and good (as was Liam Neeson), but how much money is that star-power diverting from a wider and larger dialogue system? Guys like Wes Johnson are just as skilled and ridiculously less expensive.
Though I disagree with the sentences versus topics layout. It was acceptable in FO3 because that was an old hangover from the FO series, but for TES, having my character speak in predetermined sentences is putting words in my mouth. Further, having a "Good," "Neutral," and "Evil" dialogue option for each decision choice is stepping further away from TES's moral ambiguity, as well as awkwardly typecasting my character by forcing him to respond in polar extremes. The topic system allows me to imagine how I might ask, and it allows me to avoid such good/neutral/evil typecasting. I greatly prefer it.
However, what they could do is, along with avoiding big-name spending, double their voice-acting budget (and get voice synthesizers to add small amounts of variety, thus avoiding everyone sounding the same, record at least one voice for every race and gender, and give everyone a collection of repetitive yet informative topics a la Morrowind, with different responses via region when appropriate. Then, also give everyone at least one unique line, and then take the more active NPCs and give them a lot more personalized options of dialogue. That'll be essentially the same system as FO3; important NPCs versus filler NPCs, but all the NPCs will get a lot more to say.