It pains me to say Xbox. There's so much I love about the Gamecube including a half dozen or so MUST have games and the greatest controller ever made. But an Xbox with a mod chip gives you so much.
Lilwolf....modding an Xbox doesn't make it act more like a PC except that you can run Linux on it, but relatively few people have any interest in that. Here is one example of what I do with my xbox:
My Xbox is in my living room, hooked to my home theater. My PC is in my office, but has my entire MP3 collection and my entire movie collection and my entire TV show collection (the latter two are ripped to DIVX files). When I turn on my Xbox I get a very slick menu that gives me access, not only to all the games I have sitting on the harddrive inside my xbox (about 60), but it gives me transparent access to all that media saved on my PC in the other room, which it streams to my home theater when requested. Xbox Media Center also takes the liberty of automatically downloading CD cover art from the CDDB and Movie cover art from IMDB (as well as detailed information about virtually any movie in existence). I can also run emulators to play the entire libraries of NES, Gameboy, Master System, Super Nintendo, Genesis, Playstation 1 and Nintendo 64. It even has MAME. So instead of having all my media trapped on my PC, I get to have it where it is really useful, on my sofa with surround sound and a nice TV, rather than sitting in an office chair by myself (albeit with surround sound) on my much smaller computer monitor. Oh yeah...and like I said, the games are on my xbox hard drive, so i don't even have to put a disc in the drive to play them.
Here are some screenshots of Xbox Media Center. (P.S. The software and skin you see in these pictures costs nothing)