I have all three systems.
Since my Xbox 360 is broke, I obviously can't play it. Therefore, my Nintendo Wii is getting more attention out of all of my systems.
The PlayStation 3 has a good future in my opinion, but there simply aren't many games out that interest me. I do want to get Motorstorm though, that game looks great and the demo is fun.
If my 360 was working, that's the system I'd easily play the most just because of Gears of War.