Some of the above is not entirely accurate. I work for a game developer, and am part of a multi-person audio team. I know of several other developers who have sizable audio teams. This is something that's improving throughout the industry, though it depends on the quality of the titles being produced.
Most of the games I've worked on have been big budget, "AAA" (as they call them) titles. For all of these projects, there has been an in-house audio staff of at least several people, as well as some outsourcing (VO, music, some types of sound design). It may seem as if these are the rare situations, but they're not THAT rare. If you watch the industry, there are quite a few big titles that are launched each year, and generally all of them have more than two or three sets of ears involved.
At a previous employer, we had nine audio staff (four audio-focused programmers and five audio designers/implementers) out of 110 total. At another job, we had five audio staffers (one audio-focused programmer and four audio designers/implementers) out of 130 total. I know of a few places where the numbers are greater than this.
It IS very hard to get into though. We still are among the rarest people in this industry, and due to the type of work we do (which is very granular, involves a lot of scripting knowledge, and is becoming more complicated with each console generation), experience is generally needed to get any sort of decent job. There's still a black box mentality towards audio... a lot of developers don't want to spend time training or getting someone on their feet, they just don't want to worry about sound at all.
I came from a linear post background to games. I always wanted to work in games, but couldn't get in at first. After spending a few years working in TV, I finally made it in, but it had nothing to do with my experience. It came down to having a friend in the business and being in the right place at the right time.
Making the jump is tough though. You start at the bottom, just as if I were to jump from games over to film. And the job itself is very different. It's not just making sound effects to video. You have to think about how audio is going to be separated into components and triggered from within the game. It requires some serious out of the box thinking, but that's why I love it