Our two younger sons bought a Playstation 3. They bought the 3 over a 2, even though it cost more, because you could play the old Playstation games on it, but not on the 2. Some of the things they like about it . . . the controllers have rechargable batteries, which charge while they play, and then they can disconnect from a cord for awhile; the Blu-ray DVD player; Internet connectibility; no need for memory cards with games, as the console has a good sized hard drive.
There is at least one game that requires more physical movement to play (I think it's a baseball game). Some of the games require the player to move the controller from side to side or up and down to accomplish some tasks, but it is not as interactive as the Wii.
Speaking of availability of the Wii - the local Toys-R-Us had people lined up at midnight to get the few that would be available at 7 AM the next morning. The Circuit City store right next to it got a shipment of Wiis on Christmas Eve, about 30 of them! You can bet that place was crazy!
Chester 
