I think everyone's referring to system link capable games. 16 player Halo is, of course, a bigger experience than 4 player split screen Halo. It's a big deal in college dorms and apartments, and vastly more popular than 4 player Halo obviously. Still, the Gamecube is much better suited for party games with wireless controllers and a smaller console (if you've ever had to untangle 8 or more controller wires to switch one controller to a different Xbox, you'd appreciate the wavebird).