Spider-Man 2 reportedly uses just 10% of the dialogue recorded by Venom’s voice actor
Tony Todd reveals some of the content which didn’t make the final…
The article is unnecessarily negative. While I think it's weird that they allegedly cut so much without doing rewrites, the author's guesses were grossly presumptive.
Just like movies. The sheer number of takes compared to what’s used.
I find Stephen Merchant talking about the process for recording lines for Wheatley in Portal 2
What's the common used percentage for video games? I'd imagine recording a ton more than is used would be pretty common.
Depends at what stage of development you get the recordings done (although for larger projects it's likely to be across several sessions).
The later you start the process, the fewer lines you'll have to toss out. But big studios don't mind throwing money at recording sessions, so losing 50%+ isn't that big of a deal as long as there were still some usable results.