My Wii. I've played on my PS4 for about 30 hours (28 for Fifa 14, 2 for AC IV) and even then my time played on the Wii doesn't even come close. It's the worst game related purchase I ever made. It's not even that the games are that bad, it's the system that doesn't do it for me. When I can play interesting games with good graphics, or interesting games that look like shit (or are 3D platformers, which I don't like) the choice is easy.
If I had more space to hook up all my consoles I might have played Xenoblade, but I don't, so it's not worth it.
Same for the 360, really, since most games are available on the PS3 with minimal differences. I just haven't got room to hook up an extra console. I played Mass Effect 1+2 and ToV, and that's it. It convinced me to just stick to one console this generation, and ignore the other consoles' exclusives. They may be great, but don't justify buying an entire console.