Wii U is the way to go if you like LOCAL MULTIPLAYER
The best things on Wii U so far are as follows (in no particular order)
1. Nintendo Land: Ghost Game and Animal Crossing - these are really good for friends over + beer. I think they are an underrated experience that is more fun than Wii Sports.
2. Smash U - obvious reasons.
3. Pikmin 3 COOP - the singleplayer game is kinda mehhhh but when you play with a friend, it becomes way more fun. The co-op mode is so much fun, and so addicting.
4. Mario Kart 8 - obvious reasons are obvious.
5. Super Mario 3D World - the single player experience is not as tight or fun as Super Mario 3D Land or Galaxy 1/2, BUT as a co-op / competitive game, this shit is great fun.
6. Rayman: Legends is fun single player, but a lot of fun in co-op too.
As far as single player experiences go, your options are more slim. Captain Toad, Bayonetta 2, Windwaker HD, and like... Lego City Undercover is about all I can recommend.
For me personally though, Wii U is the best console to get for multiplayer, and the PC + Wii U combo feels perfect.