Unlike the PC, which very much dominates it's own gaming market in comparison to Mac and linux gaming, console gaming is usually a very tight market. Things like pricing, availability, game libraries, display options affect which one you'll get or at least which one you'll get first. This generation I have to put in my vote for Xbox winning that race.
Really I think Nintendo won the console market again this year, but Nintendo is making sure to segment their base from that of the other two multimedia consoles, so I'm separating out the Wii and handhelds and going to the ones that are competing the most directly in terms in features. That leaves the Playstation and Xbox360 in that category.
The PS3 has a large library, with not as many exclusives as it had one generation before. The PS2 was soundly able to rise to the top with the Metal Gear Series and Final Fantasy, but this time around, FF has jumped to almost everyone, and the PS3 has only had one MGS game. Sure there have been the really good games that came out like Heavy Rain, Uncharted 2 and Infamous, but is there really anything that has sold like the Gears of War Series or Halo. I know people love God of War, but I don't know anyone who says they are still playing it, or for that matter played it much past the beginning. I do however know people who are still playing Halo 3.
Which actually brings up the best point in Microsofts favor. Live as a service is THE model for online console gaming and content delivery. Stable servers, easy to get DLC and always on people make live just leaps ahead. Sure there's the price, but you can get around that easy if you try (I mean by the year sub's on sale in stores, yes that happens), and the price isn't even that high. Every PS3 multiplayer person I've met complains about the stability of games or game matching. X360 players just complain about the map rotations, but they never find it hard to get in a game.
The lack of exclusives isn't the only thing that's hurting PS3 is my vote though. It's also the controller and the price. The Sony Dualshock is a classic, make no mistake, but the X360 controller actually works better for me in alot of situations. The feels is a bit small, somehow different from the last gen, and I find the L2 and R2 buttons are tempermental. Also I've never been a fan of their analog stick's sensitivity (across all the versions). Comparing that to the X360 controller which really feels better for shooters just makes that much of a difference. The original price also made a huge deal in my options. While both were a bit more than their previous incarnations, the PS3 was originally doing it's best Neo Geo impersonation. Even now, I can't imagine putting down $600 for the console, blue ray player or not. that price drop was the best thing you could do, especially after releasing the slim model.
Now true, there is the hardware failure rate on the X360, and I'm not going to try to justify that. Microsoft had a hard time making a gaming console that could stand up to the rigors of hardcore gaming, but a counter to that is that Microsoft made a gaming console. There were many of times during the year (not even the holiday season) that you couldn't find a PS3, not because they were sold out, but because they never came in. Even though the PS3 is a Blue Ray Player, and Microsoft backed HD-DVD, I don't find it any more endearing as a product. It may only do everything, but sometimes that can be too much.
Ultimately, it's tough to bond with a product you can never get, coupled with a higher initial price and shared games that may play as well or better on another system.