Looking at successful game franchises over the years, it's hard to argue that Halo reigns champion with Microsoft. Killer sales, rabid fans, and long-term commitments to online gameplay has put Halo on top in any incarnation over the years. Now it seems Microsoft isn't happy with only releasing a Halo title every 3 years or so.
Corporate VP of Microsoft, Phil Spencer, doesn't feel that is good enough.
We're coming up on, what, next year is the 10th anniversary. You watch the change in gamers in 10 years. The percentage of players who are playing Reach that were I'll say not old enough to play Halo 1 at the time, 10 years is a long time between launches. We definitely think about a more persistent Halo engagement for customers and not going dark for two years, and Live helps obviously with multiplayer to keep people engaged.
Imagine a world with Halo 2011 keeping up with the yearly sports release, or Call of Duty. Is a Halo-a-year too much? Or, do we just need more and more to keep ourselves busy and look forward to once a year?
Source: Uk.xbox360.ign.com