I'm not worried about the future of Nintendo. Not when they keep putting out video games of this quality. Splatoon is kind of hard to explain. You wonder if they started with the name and built it from there, or if a programmer came along and said "I've just written this great bit of code that lets you lay paint down on scenery....". Either way the game rocks.
Each player is part kid, part squid. You can play on your own, or as part of a team aiming to paint the town red (or whatever colour you've been assigned). When you change into squid mode you can move quickly through paint of your own colour. So you can spray the floors and walls in front of you and then zoom through it. You can use your "squiddiness" to go under barriers too. And of course your paint gun is pretty fatal to players shooting a different colour.
The rounds are timed and the player who has covered the most territory wins. There are some splendid weapons, including a paint roller that is horribly effective at close range. There's a story mode and lots of challenges too.
I must come clean at this point, I've not actually played it. But I watched the rest of the family having a go and much fun was had. You can do a two player mode, but you'll need some joypad like controllers, it won't work with just a second Wii controller. We used a classic controller and that worked fine.
Apparently the game works really well in network multiplayer too.