I have a Wii and an Xbox. Xbox has the largest game library of all 3 systems. I haven't bought a Kinect since I already have a Wii, that's a can of worms I don't want to open, haha!
I'm pleased with the Wii, especially since they added the gyro remote, this makes it much more dynamic.
If it's about money and just family fun, go with the Wii. If it's about serious gaming, go with the Xbox or PS3.
Plus, there's that little leak on Sony's security, hahaha! Go with Xbox over PS3