Volleyball is more of a timing game. You can't move around the full court, so a purple icon pops up when and where the ball is coming. Now within that, you can do bumps and sets, and direct the ball at a specific angle. It's not JUST "gesture when the icon appears" - sort of a hybrid.
Table tennis is solid. You can paddle with your left or right hand, move across and back from the table, it detects smashes, topspins, backhands, all sorts of hits. There seems to be a tiny bit of helpful cheating with the aim, but in general you move your paddle hand to the right point in space, and it will return the ball.
I was struggling a bit at first trying to figure out what the game expected from me. Eventually I just thought of it like I was actually playing table tennis and it worked as well as all the times I've played it in reality. Was able to move freely and hit the ball any way I wanted, in the direction I wanted. Impressive stuff, though Champion difficulty is BRUTAL (fast... so very fast...)
I tried playing while holding an actual paddle and Kinect didn't complain. That was nice, and helped to have something physical to interact with.