Xbox 360 and Xbox One:
Not enough exclusives that interest me. My main gaming system is a Desktop-PC and so even some of the console-exclusive Xbox games are available to me. Also the XBox ecosystem is too shooter/action focused for me. That of course doesn't mean that there aren't games available from other genres, but I just expect to get more of those for my PC, PS3 and PS4 in the long term. The only Xbox-exclusive games I'd really like to play are the Halo series (yes, sometimes I also play shooters), and the mainline Forza games (I'm a big Gran Turismo fan, but I'd really like to try the competition, especially since the newest Forza has a few cars I love that aren't available in GT). But 2 gaming franchises I'd really like to play and then perhaps 2 or 3 other exklusives that I'm only somewhat interested in, aren't enough for me to put a few hundred euros down. Both are still great consoles though, and I like playing them at a friend of mine.
Wii:
Not too interested in the motion controlled games. I don't hate motion based games (heck, I even have two Playstation Move controllers), but there are just too many Wii games going in this direction for me. Also Nintendo kinda lost me with their short life time for the Gameboy Advance. It was the first Gameboy I had and I bought it like 1 or 2 years after its release, but the system was dead just a few years later with the release of the DS. So I think that I was kinda angry at Nintendo for that. I just expect longer support with new games.
Still there are some games from the Wii that I'd like to play: Mario Galaxy 1 and 2, Mario Kart Wii and Xenoblade Chronicles.
Wii U:
Still waiting for another price drop to be honest. Shortly after its release the 8GB model was available for 179€ (excluding the sensor bar), and I don't want to buy it for higher price than that (currently it's available for 219€). Especially since the pack including a sensor bar + remote plus with nunchuck increased from ~40€ to ~70€ since then. I will bite once I can have a Wii U + Sensor Bar + Remote Plus + Nunchuck for 200€. If it's the 8GB or 32GB version doesn't really matter since I won't buy digital games for a Nintendo system anyway because of their stupid console-ID locked system. I'm also not really interested in the Wii U Gamepad, and would also buy a version of the console that exchanged it with a Pro Controller at the same price, if the games I'm interested in would be changed in a way not requiring the Gamepad anymore.
But all in all I'm pretty sure that I will buy a Wii U in the next 1 or 2 years, and I'm already excited to play some of the Wii games I missed and the Wii U exclusives I'm interested in: Super Mario 3D World, Mario Kart 8 and Xenoblade Chronicles X and maybe the Zelda games.
Another reason why I don't buy all of the stationary consoles is that I've limited space under my TV and only 3 HDMI connections. I also don't want to switch HDMI cables, so there can be a maximum of 3 systems connected to my TV. Currently those are my old notebook (to play some emulated games with improved grahpics; but the notebook can't handle more than DC or PSP games), my PS3 and my PS4. My Ouya had to go once I bought the PS4 and I will gift my PS3 to my sister's family once I finished the remaining games I want to finish. So one spot for another system will then be open. At the moment the Wii U has the highest chance to take this spot (and an android device may replace my notebook).
Handhelds:
Not a big fan of handhelds anymore. I just prefer reading a book or magazine when I'm on the go. I bought a PS Vita to play a few of the PS+ games I got, but now I'm just using it to remote play some of my PS4 games when lying in bed. Not worth the ~200€ I paid for the handheld + 32GB memory card + grip, though.