For all of you completely forgetting the highly rated and great games that couldn't be found on any other console this year for the 360:
Gears of War 3
Forza 4
Dance Central 2 (yes it's Kinect, but it's a great game and isn't meant to be hardcore)
Mortal Kombat
Halo CE: Anniversary (relaunch, but still awesome)
Bastion (console exclusive)
Radiant Silvergun
-then take all those big games like Battlefield 3 and MW3 and see how much more popular they are on the 360 than any other console AND the fact that MS gets first DLC dibs. Plus the 360 sold 1.7 mil units in the US in November (record-setting 1 mil units sold the week of Thanksgiving). Shows you how many people are flocking to the 360 as it does multimedia & gaming so well. And don't diss Kinect. It doesn't have a ton of good games, but it has several and the technology alone is #1.
Why keep a PS3? Well if you haven't played Uncharted, Infamous, etc and never really intended to, then there's absolutely no reason to keep your PS3 as those are most of the games worth playing on that console. This next year doesn't lend incentive to continue PS3 fanboy-tendencies, whereas 2012 has some big and promising titles coming for the 360 only (Halo, Ryse, Witcher 2, etc). Again, if you aren't big on the couple of strong titles that launched this year only on the PS3, then ditch your PS3.