I own a 360, Wii U, 3DS, Windows Phone. Did want to get a PS3 to play some of the exclusives (Littlebigplanet, God of War, Last of Us). But I barely have time to play the games I have and its probably not a good idea to take on anymore new systems at this point. To be honest, my 3DS takes up most of my time. Especially now with Animal Crossing. That will soon be followed by Pokemon X and Y.
And I'm not a big multiplayer fan. Maybe a game of Madden with online once in awhile. But I hate having to rely on someone else or having someone else rely on me to game. I rather play a game and play it the way I want. That or playing with a friend who's physically present.