Agreed. Halo, one of the greatest games of modern multimedia, would be fine, as long as you figure out connections to preferably two of the poems. You need quotes as well, so it might be an idea to get the transcript from somewhere. Or you could play it multiple times. Your choice.
Definition of 'Area of study' from the ETA website: "exploration of a concept that affects our perceptions of ourselves and our world." And, link that to this extract from HSC online about text: "Related material is any additional text from any genre, whether it is fiction, poetry, drama, film or multimedia that can be used in conjunction with your focus area." So, yes. Games included.
But I would be careful about how you go about it. Games are tricky bussiness, and though it's best to analyse it much like you would a film, the gameplay and lack of direction make things hard [that is, you can't start it up and say "I want to look at THIS" you actually have to get there, which can be pretty damn hard and time consuming]. Also, you're dealing with old teachers. People who don't play games and don't know exactly how they work. They know films and maybe a few know music from this era, but games are something almost foreign. Still, they don't care, they're analysing your essay, not your favourite game.
So, in conclusion, I have, not halo, and it works fine. Go for it.