Well according to IDC, no one. In a press release, the analysts acknowledge that this generation of gaming/entertainment devices have - to a certain extent - defined their own market niche and will each share a significant portion of our wallets.
To quote the press release:
“IDC says Microsoft's Xbox 360 was the best selling current generation console for 2006 because it enjoyed a full year lead in the market. Microsoft is relishing in the PS3's launch slip-ups, where PS3 supply deficits diminished profits. The battle is heating up between the 360 and PS3, as the two gaming manufacturers target the same hardcore/enthusiast gamer to dominate the market.
Nintendo, on the other hand, is the only one of the three manufacturers working to grow its total accessible market for its hardware and software by broadening its audience beyond the traditional market. Nintendo has designed its latest hardware and software to be more inviting and fun, and less intimidating for non-gamers including those who may never self-identify as a gamer. Nintendo also enjoys support from the fan base it has captured with successful first party franchises. IDC believes hardware shipments of Nintendo's Wii will capture a little more than a third of the worldwide market by 2008, rising slightly above Sony's PS3 and Microsoft's Xbox 360. “
Not that it really matters, however the IDC report – like a lot of people in the media and seemingly game enthusiasts themselves are obsessed about who will “win” this sales race:
“Who will win? IDC says none of the three new consoles will dominate the market in the next five years like the PS2 dominated last cycle; however, Nintendo's Wii will outship and outsell the 360 and PS3 in 2007 and 2008.”
Of course sales are important only from the point of view of software support. If you are on a winner, then likely your experience will be supported by the manufacturer and third parties alike. So good luck in your choice of entertainment electronics.