In an interview done by Gamesindustry biz Microsoft's chief financial officer, Chris Liddell, has confirmed that the company expects platform exclusive Halo 3 to boost Xbox 360 sales when the game hits the shops later this year. He states:
"Halo 3 is clearly going to have a positive impact in two senses. One, it gives us more confidence in the number of consoles we think we're going to be able to sell next year."
He also adds that :
"In terms of the direct impact, obviously it's a first-party product so it's reasonably profitable from our point of view, and it will be several hundreds of millions of dollars of revenue next year."
This might in fact be true because of the enormous fanbase for the halo franchise