Bronco, I felt the same way about my Gamecube. And I imagine since you have kids, its especially great since Nintendo focuses on being open for the young'uns.
However, I needed another DVD player for my living room about a year ago, so I ended up picking up an Xbox (You can get an xbox for $119 new after rebate now). My gamecube has been gathering dust ever since.
I've tried to get friends of mine interested in online PC gaming with me, but its just not that social. But with an xbox, I've gotten them interested in gaming again. We'll have poker/Halo nights, and I'll connect with them during the week to play Rainbow Six 3 coop. During more mixed crowd parties (ie. not just guys), I'll whip out the DDR pads and we'll have a good time laughing at each other's moves.
I have a blast with Project Gotham Racing 2, even though in the past I haven't liked racing games. The single player is addicting and its a lot of fun to play online. Crimson Skies was a great purchase for the polished single player game and I've just picked up Chronicles of Riddick, the graphics are amazing and the game is engrossing. I haven't picked up Full Spectrum Warrior yet, but I've heard great things about the coop mode on Xbox Live, so I hope to grab it at some point.
I've just mentioned the Xbox Only games, but I enjoy a lot of multi-console games, and I buy them for the xbox due to its harddrive and better graphics. And if its a PC/Xbox game, I'll grab it for the Xbox, so when buddies are over, we can play it together, or I can lounge on my couch playing through the game and my wife will actually watch the storyline.
I do hope to eventually pick up Mario Kart, but many other Nintendo games I bought, I ended up never finishing, Zelda, Metroid, Mario. Nintendo just lost its magic for me. I did buy it solely for Rogue Squadron 2, which I completed, and my wife loved Pikmin. But the Cube is gathering dust now, and Halo coop has been my favorite console experience this generation, my wife and I are about to go through Halo all over again. It reminds me of the old Contra coop goodness.