I'm going to give it a solid 7. This game wasn't as mindblowing as a lot of games this gen but I'm willing to bet that, while other games become unplayable, Wii Play will still be just as fun as it ever was. The controls are responsive and in a lot of ways, I think this game is better than Wii Sports. It's just a bunch of mini-games but, in small doses, those games are cool.
Nintendo Channel says I played Wii Play: 41 hours, 3 minutes. Played 49 times.
Nintendo Channel says I played Wii Sports: 35 hours, 49 minutes. Played 38 times.
The only games I've played more than these two games on my Wii are Super Mario Galaxy, Wario Ware, and the Internet channel. I think that says a lot.