Sony was launched in Japan on 11th Nov and on 17th Nov. in North US while Wii debuted in US on 19th Nov. Nintendo let out the sales figures that say more than 600,000 Wii units have been sold in just eight days while Sony could afford just 200,000 PS3 units in past days.

Colin Sebastian, Lazard Capital Markets analyst commenting on Microsoft's current business stats says after one year of its debut Xbox 360 is still selling above average while XBLA titles like GOW are catching speed on sales track. He said the Xbox360 is headed for its 10 million unit's transaction worldwide by the end of this year and Microsoft will effortlessly manage it.
Looking the new launches in the market like; Wii and PS3, it has affected the sale of Xbox360 negligibly until now. Microsoft has pimped out the great download event on 22nd of Nov. that will also considerably contribute to the sale figures of Xbox360. Moreover, hardly a week ago Micro Center was selling off Xbox 360 for retail price $100 less than real price but unfortunately the offer was available on just 1000 Xbox360 units.
The shortage of newly launched consoles in the market are also helping Xbox 360 sale as Sony had confirmed 400,000 PS3 units for US launch day but could afford just half of the total no. i.e. 200,000 units. However the true results are still to come but one thing is clear that Xbox 360 sales figures have been hindered by the release of new next-gen consoles not at all.
Via: next-gen