Microsoft's system seller Halo 3 sold more than 5 million copies, according to GameDaily.com, while BioWare's newly launched Mass Effect reached the homes of more than 1 million Xbox 360 owners.

GameDaily reports that Jeff Bell, Corporate Vice President of Global Marketing for the Xbox 360 at Redmond, confirmed the amazing results for the third installment in the Halo trilogy. If we are not surprised by the success Masterchief's last adventures had, the nice surprise is BioWare's Mass Effect.

According to Bell, the RPG released on November 20th sold almost 1 million copies in less than 3 weeks, which beats even the most optmistic estimates."We've... seen a strong response to both Halo 3 sales with more than 5 million, and Mass Effect which has sold more than a million copies in less than three weeks," said Microsoft's official.

The aforementioned site later obtained confirmation that the numbers refer to worldwide sales for both titles.

However, the difficulty that pops out for Microsoft is the recent acquisition of BioWare by Electronic Arts. While Microsoft holds the exclusive rights to publish Mass Effect on the Xbox 360 (including future sequels), EA now holds the rights to develop the valuable IP. Microsoft is of course interested in keeping Mass Effect an Xbox 360 exclusive, and has repeateadly stated that "we'll be talking to EA and BioWare in the weeks to come," but EA's policy concerning blockbusters is to have them "multi-platformed".

With almost 1 million copies sold in less than a month and with positive reviews from most gaming sites across the Web, BioWare's creation is on track of becoming another platinum Xbox 360 hit, just like Gears of War was last year, and just like Halo 3 is now. That will make Microsoft's negotiations with EA even more interesting, but hey, it's in the best interest of consumers right?