Something to consider. Getting a WiiU also nets you a Wii. You may have the AES / MVS versions already, but the Wii does have a huge amount of retro games on its virtual console. The WiiU has earthbound. And its rather nice to play some of these classics on the WiiU pad.
The WiiU has some of the best platformers from its Wii BC and for the WiiU.
It has as other people said the best version of Bayonetta, Sonic Racing, and Deus X
Smash Brothers WiiU is amazing, Tekken WiiU is worth it just to see Heihachi in a mario costume.
PS4 may get some decent titles next year making it a more interesting sell, but considering its current library, I'd wait and see, they may reduce price.
Another option is the Vita. It has a lot of amazing niche japanese games for it, and it also lets you play a decent chunk of PS1 titles and PSP titles.
I also think the WiiU games will become rare and collectable in the years to come. The system is selling worse than dreamcast, so I doubt there are huge production runs of its games. So its library will probably end up like the Saturn's games, some will become dirt cheap, but all the good games may fetch Saturn-like prices. (Around $200 to $300 ).
Horii also made a solid fight stick for the Wii, which does work with WiiU titles.