He offered some tips for producers hoping to get their games on the service. They include:
* Gameplay that is immediately obvious to the player.
* Multiplayer options that include co-op play. "Co-op is crucial in the broadening effort," said Sullivan.
* A worldwide appeal -- not just North America.
* Appealing graphics.
* Downloadable content options.
* Tie-ins with orther products or games.
He said 65 percent of Xbox Live users had downloaded an Xbox Live Arcade game, with downloads now at 5 million. The conversion rate is still about 20 percent (demo to purchase) compared with less than 2 percent in the PC market. "This is blowing away anything in the PC space," he said, explaining why the service is so popular with developers.
The top games are now Geometry Wars, Uno, Marble Blast Ultra, Gauntlet and Zuma.