Of course they can - anything's possible as they say... it's just that they're going to find it a very difficult battle IMHO particularly when you really think about Wii outselling 360 WW so quickly and PS3 already outselling it most weeks WW despite its head start.
The other problem for MS is if they overly try and court casual gamers they run the risk of losing their core fans. Many posts I've seen since E3 grumbled about the focus on Avatars and Lips (i.e. copying Wii and PS3 approaches) vs focusing on core 360 gamers.
Try to be reasonable... its easier than you think...







