For all the talk about the Wii being underpowered, I have to say it's still FUN, which is the point. I play older PC games, Super Nintendo emulators, online flash games, etc because they're fun, even if none of the graphics are bleeding edge. Compare that to PS3 games that might be very very pretty, but only an inch deep and 3 hours long.
A Nintendo Wii with Mario Galaxy, Metroid Prime, Smash Bros, Mario Kart, Twilight Princess, Lego Star Wars, etc can be a heck of a lot of entertainment, and for a lot cheaper than an XBox 360 and its games. Sure, it's not Halo, or Gears of War, or Oblivion, but it's a great system for someone who just wants to have fun with two or three friends.
Nintendo absolutely hit it out of the park this generation with the choice to be different (motion sensing), focus more on fun than graphics, and hit the price sweet spot.