Here are three steps to better voice acting in games:
Video games are b-movies. There's nothing wrong with that. I love b-movies. At their best, the point of a b-movie is that it's inclusive. It says: the people who made this are a lot like you. Remember when you thought that a fight between a werewolf and a cyborg leprechaun would be awesome? We thought so too. And because we only had $20 in our budget for it, we need a little help from you to make it work: if you can suspend your disbelief for an hour or so, this is gonna be great.
B-movie dialog is not good, in any kind of objective quality sense. But it's written with a kind of hard-edged desparation. For most b-movies, the only reason to have dialog is to find a way to either explain or lead into the next fight (werewolf vs. mutated shark! awesome!). Perversely, this singlemindedness often translates into less padding, fewer monologues, slimmer storytelling. Again, it's not good. But it knows why it's there, and it suffers no illusions of its own brilliance.
And that's the point. The typical video game operates on exactly the same goals as the b-movie, except that you get to choreograph the fight between the werewolf and the alien motorcycle (yes!). "Better" dialog doesn't mean exposing universal truths. It just means that if it ever gets in the way of the viewer/player/reader who just wants to enjoy some irritable lycanthropes, it needs to go.
I've spent a couple of years now recording non-professional voice talent for multimedia projects, and it's been educational. I've learned the little tricks to getting a decent, inoffensive performance out of people who have no real business being in front of a microphone. It's not usually great. But it's not terrible, either. I don't think there's much excuse for bad voice-acting. But I suspect the real problem is not that the voice talent is bad, so much as they're being forced on you through an excess of terrible writing.
Who else wants to talk?