***“Games with Gold” free games offer available 6/10/13-12/31/13 for qualifying paid Gold members only. Xbox 360 games (selected by Xbox) available for free download from Marketplace only during specified half-month window; available games may vary by country. Some titles may only be available for download by account holders 18+. Kinect and/or hard drive required for some games. See xbox.com/live
They've already said that the games will come until the Xbox One is released, and that's been announced with a November release date. The only reason for the 12/31/13 date is because after that they're going away.
It's a nice gesture, though odd just prior to a new console's release, but personally, I do prefer the more current games PS+ has given me as opposed to free games I played years ago. Saying "hey look I got a $5 used game for free from M$ nah nah nah PS+ people!" seems pretty stupid...when they get games like Sleeping Dogs, Saints Row 3, Spec Ops The Line, Vanquish, Xcom, etc for "rentals"... It's still nothing compared to PS+, but I'll take free games regardless!