I've written here before about how much I love my XBOX 360, but recently I haven't been using it very much to listen to music or view photos on the TV. Halo 3 for the XBOX 360 launched a week and a half ago, and I have to admit all of my free time since then has been spent in front of my TV with a controller in my hand. Everything about it rules, but the multiplayer aspect is the best. I'm not sure exactly why other game companies don't just copy what Bungie Studios does with Halo, but it is hands down the best online multiplayer game on a console.
But from a dad's perspective beware, this isn't a game for kids. It's a violent shoot-em up that, while fun, probably isn't appropriate for small children. Also, if you've got a son (or daughter? but I doubt it) playing the game at home and online, know that the language among the players might not be what you would ideally want him to hear. But then again, if he's playing Halo 3 online, it probably isn't anything he hasn't heard before.
So if you're a dad and you've got an XBOX 360, it's a must-own game. In fact, it's probably worth buying an XBOX 360 for too.
And if you don't have an XBOX 360 yet, you can always pick up an XBOX 360 Elite system at Amazon.com.